TWI886964B - Active noise cancellation integrated circuit and active noise cancellation method for stacking at least one anti-noise signal and at least one non-anti-noise sifnal, and active noise cancellation headphone - Google Patents

Abstract

The present invention relates to an active noise cancellation integrated circuit for stacking at least one anti-noise signal and at least one non-anti-noise signal, an associated method, and an active noise cancellation headphone using the same. The method is applicable to an audio playback device with at least one ANC filtering unit and at least one non-ANC filtering unit, and includes: acquiring a non-anti-noise signal from a non-ANC filtering unit; generating a decoupled signal by processing the non-anti-noise signal with the transfer function of a physical channel and operations of an ANC filtering unit; performing a signal superposition, wherein an anti-noise signal from the ANC filtering unit is superposed with the decoupled signal; and performing an audio playback based on the superposed signal and an audio signal such that noise is eliminated.

Description

Active noise reduction integrated circuit and active noise reduction method capable of stacking at least one anti-noise signal and at least one non-anti-noise signal, and active noise reduction earphone

The present invention relates to a noise reduction technology, in particular to an active noise reduction integrated circuit, method and active noise reduction earphone using the same that can stack at least one anti-noise signal and at least one non-anti-noise signal.

The noise reduction technology of general headphones can be divided into passive noise cancellation (PNC) and active noise cancellation (ANC). Passive noise cancellation mainly isolates noise as much as possible through the sound insulation material or special structure of the headphone. Generally, it is in-ear headphones or over-ear headphones. Long-term wearing will cause ear swelling and pain, and excessive sound pressure will even affect hearing. Active noise cancellation is to set up a special noise reduction circuit in the headphones. Generally, it receives and analyzes external noise through an audio receiver (such as a micro microphone) and an anti-noise output chip, and generates an anti-phase sound wave, which offsets the noise through the destructive interference of the sound wave.

In addition, the above active noise reduction is generally divided into feed-forward ANC, feedback ANC and hybrid ANC. Feed-forward ANC is to place the noise reduction microphone on the outside of the earphone, receive the noise outside the earphone through the microphone, and process it through the digital signal processing integrated circuit to convert it into an anti-noise signal. Feedback ANC is to place the noise reduction microphone on the inside of the earphone, receive the sound signal in the ear canal of the user, and feed it back to the digital signal processing integrated circuit to generate an anti-noise signal. In addition, composite noise reduction uses two or more noise reduction microphones to receive noise, and generates multiple anti-noise signals through different digital signal processing integrated circuits, and then superimposes the sound wave signals to offset the noise.

Since sound waves are generated by multiple microphones at different locations and different signal processing, the final observation point receives multiple sound waves superimposed, which leads to unwanted compensation and makes the human ear hear the audio playback with deteriorated quality. In view of this, how to reduce or eliminate the deficiencies in the above-mentioned related fields is indeed a problem to be solved.

The present invention provides an active noise reduction headset, which includes an audio conversion device and an active noise reduction integrated circuit of an embodiment of the present invention that can stack at least one anti-noise signal and at least one non-anti-noise signal. The active noise reduction integrated circuit that can stack at least one anti-noise signal and at least one non-anti-noise signal includes a first path, outputs a first path non-anti-noise signal, wherein the first path non-anti-noise signal is converted into a first signal by a physical channel, and the first path includes: A non-active noise reduction filter unit for generating a non-anti-noise signal; a second path for receiving an error signal containing a component of the first signal and outputting a second path anti-noise signal to the physical channel, the second path comprising: an active noise reduction filter unit for generating an anti-noise signal, wherein the anti-noise signal derives the second path anti-noise signal; and a first decoupling unit for removing the component of the first signal in the second path based on the non-anti-noise signal.

The present invention also provides an active noise reduction method capable of stacking at least one anti-noise signal and at least one non-anti-noise signal, which is applicable to an audio playback device having at least one active noise reduction filter unit and at least one non-active noise reduction filter unit. The active noise reduction method capable of stacking at least one anti-noise signal and at least one non-anti-noise signal comprises: providing a first path, outputting a first path non-anti-noise signal, wherein the first path non-anti-noise signal is converted into a first signal by a physical channel, and the first path comprises: a non-active noise reduction filter unit; A unit is provided to generate a non-anti-noise signal; a second path is provided to receive an error signal containing a component of the first signal, and output a second path anti-noise signal to the physical channel, the second path includes: an active noise reduction filter unit to generate an anti-noise signal, wherein the anti-noise signal derives the second path anti-noise signal; based on the non-anti-noise signal, the component of the first signal in the second path is removed; and based on the first path non-anti-noise signal and the second path anti-noise signal, the first path non-anti-noise signal and the second path anti-noise signal are played to eliminate noise.

The spirit of the present invention is to set at least one active noise reduction filter unit and at least one non-active noise reduction filter unit in the active noise reduction device of the active noise reduction headset. Furthermore, the redundant components generated by other active noise reduction filter units caused by the output signal of each active noise reduction filter unit are eliminated by decoupling. Therefore, with the help of the decoupling technology provided by the present invention, the side effects caused by the active noise reduction filter can be reduced or suppressed, thereby achieving the expected purpose of the non-active noise reduction filter (for example, a hearing aid filter, a transparent filter or a personal sound amplification filter).

Other advantages of the present invention will be explained in more detail with the following description and diagrams.

101:Left wireless headset

102: Right wireless headset

103: Mobile devices

19: Headphone case

20,110,170: Active noise reduction integrated circuit

21: Audio conversion equipment

201:First Microphone

202: Second microphone

203: The first active noise reduction filter unit

204: Second active noise reduction filter unit

205,72: Physical channel

301: Noise

302: Only the noise suppression result of the first active noise reduction filter unit 203 (Feed Forward, FF) is turned on

303: Only the noise suppression result of the second active noise reduction filter unit 204 (Feedback, FB) is turned on

304: Expected noise suppression results of turning on the first active noise reduction filter unit 203 and the second active noise reduction filter unit 204 (FF+FB)

305: The actual noise suppression result of turning on the first active noise reduction filter unit 203 and the second active noise reduction filter unit 204 (FF+FB)

40,50,60: first decoupling unit

70,80: Second decoupling unit

401,501: First channel analog filter

402,503,603: First addition circuit

502,601: The third active noise reduction filter unit

504,604,702: Second addition circuit

601: The third active noise reduction filter unit

701: Second channel analog filter

602,801,901: Channel simulation filter

603: First adding circuit

604,702,802: Second addition circuit

91: The third active noise reduction filter unit

90: Third decoupling unit

1103: Non-active noise reduction filter unit

1703: First filter unit

1704: Second filter unit

S1001, S1002, S1003, S1601, S1602, S1603: Steps

Figure 1 is a schematic diagram of an active noise reduction headset of a preferred embodiment of the present invention.

Figure 2 is a schematic diagram of the equivalent sampling time block of an active noise reduction headset of a preferred embodiment of the present invention.

Figure 3 is a comparison diagram of the noise suppression results of the embodiment of Figure 2.

Figure 4 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset with good isolation between the ear canal and the environment, which is a preferred embodiment of the present invention.

Figure 5 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset with good isolation between the ear canal and the environment, which is a preferred embodiment of the present invention.

Figure 6 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset with good isolation between the ear canal and the environment, which is a preferred embodiment of the present invention.

Figure 7 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset that does not have good isolation between the ear canal and the environment, which is a preferred embodiment of the present invention.

Figure 8 is a schematic diagram of the equivalent sampling time block of an active noise reduction headset of a preferred embodiment of the present invention.

Figure 9 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset with good isolation between the ear canal and the environment, which is a preferred embodiment of the present invention.

Figure 10 shows a flow chart of an active noise reduction method capable of stacking multiple anti-noise signals in a preferred embodiment of the present invention.

Figure 11 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset with good isolation between the ear canal and the environment, which is a preferred embodiment of the present invention.

Figure 12 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset with good isolation between the ear canal and the environment, which is a preferred embodiment of the present invention.

Figure 13 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset with good isolation between the ear canal and the environment, which is a preferred embodiment of the present invention.

Figure 14 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset that does not have good isolation between the ear canal and the environment, which is a preferred embodiment of the present invention.

Figure 15 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset with good isolation between the ear canal and the environment, which is a preferred embodiment of the present invention.

FIG. 16 is a flow chart of an active noise reduction method for superimposing at least one anti-noise signal and at least one non-anti-noise signal according to a preferred embodiment of the present invention.

Figure 17 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset located between the ear canal and the environment, which is a preferred embodiment of the present invention.

The following description is a preferred implementation method for completing the invention, and its purpose is to describe the basic spirit of the invention, but it is not intended to limit the invention. The actual content of the invention must refer to the scope of the subsequent claims.

It must be understood that the words "include", "comprising" and the like used in this specification are used to indicate the existence of specific technical features, values, method steps, operation processes, elements and/or components, but do not exclude the addition of more technical features, values, method steps, operation processes, elements, components, or any combination thereof.

The words "first", "second", "third" etc. used in the claims are used to modify the elements in the claims, and are not used to indicate a priority, a precedence relationship, or that one element precedes another element, or the temporal sequence when performing method steps. They are only used to distinguish elements with the same name.

It must be understood that when an element is described as being "connected" or "coupled" to another element, it can be directly connected or coupled to other elements, and there may be intermediate elements. Conversely, when an element is described as being "directly connected" or "directly coupled" to another element, there are no intermediate elements. Other words used to describe the relationship between elements can also be interpreted in a similar way, such as "between" versus "directly between", or "adjacent" versus "directly adjacent", etc.

FIG. 1 is a schematic diagram of an active noise reduction headset of a preferred embodiment of the present invention. Please refer to FIG. 1. In this embodiment, a wireless earbud is used as an example. The wireless earbud is a pair of devices with wireless communication capabilities, including a left wireless earbud 101 and a right wireless earbud 102. There is no physical line connecting the left wireless earbud 101 and the right wireless earbud 102. The mobile device 103 and the left wireless earbud 101 and the mobile device 103 and the right wireless earbud 102 can use wireless communication protocols to transmit voice packets or music packets of the carrying user, such as Bluetooth's advanced audio distribution profile (A2DP) packets.

In other embodiments, other peer-to-peer (P2P) wireless communication protocols such as Wi-Fi Direct can also be used between the mobile device 103 and the left wireless headset 101, and between the mobile device 103 and the right wireless headset 102, but the present invention is not limited thereto.

In the above embodiments, the active noise reduction headphones are exemplified by wireless headphones, but those with ordinary knowledge in the relevant technical field should know that the active noise reduction headphones can also be implemented as wired headphones, and the present invention is not limited to this.

FIG. 2 is a block diagram of an equivalent sampled-time of an active noise reduction headset of a preferred embodiment of the present invention. In this embodiment, the active noise reduction headset is an in-ear headset. Referring to FIG. 2 , the active noise reduction headset includes an active noise reduction integrated circuit 20 and an audio conversion device 21. The audio conversion device 21 in this embodiment includes a first microphone 201, a second microphone 202, and a speaker (not shown). In the embodiment of the present invention, for the sake of convenience, a dotted outer frame is used as an illustrative example, and the inside of the dotted outer frame represents the interior of the headset housing 19. Among them, the first microphone 201 is outside the dotted line, indicating that the first microphone 201 is arranged outside the ear canal to receive noise outside the ear canal, and the second microphone 202 is inside the dotted line, indicating that the second microphone 202 is arranged inside the ear canal. In the following embodiments, this dotted line frame is used as a representation, but this dotted line is not used to limit the configuration of the components of the present invention.

The first microphone 201 is disposed outside the earphone housing 19 and is mainly used to receive external noise signals of the in-ear earphone. The external noise signal captured by the first microphone 201 is converted into an electrical signal after orientation and analog-to-digital conversion and input to the active noise reduction integrated circuit 20. The first microphone 201 can be called a reference microphone.

The second microphone 202 is disposed inside the earphone housing 19 and between the earphone housing 19 and the eardrum, and is mainly used to receive noise and echo in the user's ear canal, that is, ear canal echo. The earphone housing 19 is used to provide passive noise reduction. For example, the earphone housing 19 includes earphone sound insulation material. More specifically, the second microphone 202 is used to receive sound signals in the user's ear canal. The sound signal captured by the second microphone 202 will be converted into an electrical signal and input to the second active noise reduction filter unit 204. The second microphone 202 can be called an error microphone.

The active noise reduction integrated circuit 20 is used to generate an anti-noise electrical signal based on the electrical signal obtained through the first microphone 201 and the electrical signal obtained through the second microphone 202. The digital anti-noise electrical signal is converted into an anti-noise signal through, for example, a digital-to-analog converter, a reconstruction filter, a power amplifier, and a speaker transmission in sequence. For analysis, the aforementioned transmission will be presented as a transfer function. In short, the anti-noise electrical signal is converted into an anti-noise signal through the aforementioned transmission transfer function. Accordingly, if the aforementioned transmission transfer function is to be evaluated, it is necessary to be based on the anti-noise electrical signal and the anti-noise signal.

However, in practice, it is not possible to directly obtain the anti-noise signal. A possible alternative is to receive the anti-noise signal through the second microphone 202 in the absence of an external noise signal, and convert the anti-noise signal into another electrical signal in analog form. The other electrical signal is, for example, sequentially converted into an electrical signal in digital form through a preamplifier, an anti-aliasing filter, and an analog-to-digital converter, and the electrical signal replaces the anti-noise signal to evaluate the transfer function.

Although the transfer function obtained in the alternative method involves not only the transmission from the active noise reduction integrated circuit 20 to the input of the second microphone 202, but also the transmission from the output of the second microphone 202 to the active noise reduction integrated circuit 20, in order to simplify the analysis, this transfer function can be used to represent the transmission from the active noise reduction integrated circuit 20 to the input of the second microphone 202, which is represented by the physical channel 205. It should be noted that the physical channel 205 includes the above-mentioned speaker. In short, the anti-noise electrical signal output by the active noise reduction integrated circuit 20 is converted into an anti-noise signal through the above-mentioned physical channel 205.

On the other hand, the external noise signal enters the inner side of the headphone housing 19 from the outer side of the headphone housing 19 and finally reaches the second microphone 202. This transmission is the primary path, not shown. For analysis, the primary path will be presented as a transfer function. In short, the external noise signal is converted into a residual noise signal through the transfer function of the primary path. Accordingly, if the transfer function of the primary path is to be evaluated, it is necessary to be based on the external noise signal and the residual noise signal.

However, in practice, it is impossible to directly obtain the external noise signal and the residual noise signal. A possible alternative is to receive the external noise signal through the first microphone 201 and convert the external noise signal into another electrical signal in analog form. The other electrical signal is, for example, sequentially converted into a digital electrical signal through a preamplifier, an anti-aliasing filter, and an analog-to-digital converter, and the electrical signal replaces the external noise signal to evaluate the transfer function of the main path. On the other hand, the residual noise signal is received through the second microphone 202 in a situation where the active noise reduction integrated circuit 20 is disabled, and the residual noise signal is converted into another electrical signal in analog form. The other electrical signal is, for example, sequentially converted into a digital electrical signal through a preamplifier, an anti-aliasing filter, and an analog-to-digital converter, and the electrical signal replaces the residual noise signal to evaluate the transfer function of the main path.

When the active noise reduction headset is actually in operation (that is, when the active noise reduction integrated circuit 20 is enabled), the anti-noise signal interferes with the residual noise signal to achieve the effect of active noise reduction.

The active noise reduction integrated circuit 20 includes a first path and a second path.

The first path receives the output signal from the first microphone 201 and outputs a first path anti-noise signal to the physical channel 205. The first path anti-noise signal is converted by the physical channel 205 into a first signal for eliminating noise.

The second path receives the output signal from the second microphone 202 and outputs a second path anti-noise signal to the physical channel 205. The second path anti-noise signal is converted by the physical channel 205 into a second signal for eliminating noise.

The first path includes the first active noise reduction filter unit 203. Specifically, the first path starts from the output end of the first microphone 201, passes through the first active noise reduction filter unit 203, and reaches the input end of the physical channel 205.

The second path includes a second active noise reduction filter unit 204. Specifically, the second path starts from the output of the second microphone 202, passes through the second active noise reduction filter unit 204, and reaches the input of the physical channel 205.

In the embodiment of FIG. 2, the first active noise reduction filter unit 203 generates a first anti-noise signal y'1 ( n ) after filtering the electrical signal output by the first microphone _201. The first anti-noise signal y'1 ( n ) is used as the first path anti-noise signal in this embodiment. The weight of the first active noise reduction filter unit 203 is marked as W1 in FIG. _2. The first active noise reduction filter unit 203 can be implemented in a variety of ways, such as using general-purpose hardware (e.g., a microcontroller unit, a digital signal processor, a single processor, a multi _- processor with parallel processing capabilities, a graphics processor or other processors with computing capabilities), and providing the function of active noise reduction filtering when executing software and/or firmware instructions.

The second active noise reduction filter unit 204 filters the electrical signal output by the second microphone 202 to generate a second anti-noise signal y'2 ( n ). The second anti-noise signal y'2 ( n ) is used as _the second path anti-noise signal in this embodiment. The weight of the second active noise reduction filter unit 204 is marked as W2 in FIG. _{2. The} second active noise reduction filter unit 204 can be implemented in a variety of ways, such as using general-purpose hardware (e.g., a microcontroller unit, a digital signal processor, a single processor, a multi-processor with parallel processing capabilities, a graphics processor, or other processors with computing capabilities), and providing the function of active noise reduction filtering when executing software and/or firmware instructions.

In this embodiment, the first anti-noise signal y ' ₁ ( n ) and the second anti-noise signal y ' ₂ ( n ) are respectively input to the physical channel 205. However, the present disclosure is not limited thereto. In some embodiments, the first anti-noise signal y ' ₁ ( n ) and the second anti-noise signal y ' ₂ ( n ) can be added in the digital domain, and the summed anti-noise signal is input to the physical channel 205.

The audio conversion device 21 converts the first anti-noise signal y'1 ( n ) and _the second anti-noise signal y'2 ( _n ) into sound signals through the physical channel 205, and synthesizes them into a noise reduction signal (that is, the aforementioned anti - noise signal). When this noise reduction signal is actually transmitted in the ear canal, it will produce echo interference due to the reflection and attenuation of the sound waves in the ear canal. In other words, the noise reduction signal will reach the user's ear and the second microphone 202 through a physical channel in a real environment.

In this embodiment, the active noise reduction device 20 that can stack multiple anti-noise signals, for example, has a dual anti-noise system, that is, it has two active noise reduction filter units 203 and 204, which can output two noise reduction signals accordingly. The mutual interference of the two noise reduction signals is generally expected to achieve a further noise suppression effect. However, this is not the case in practice, as detailed in Figure 3. Please refer to Figure 3, which is a comparison diagram of the noise suppression results of the embodiment of Figure 2.

As shown in FIG. 3 , the vertical axis represents the magnitude and the horizontal axis represents the frequency. Reference numeral 301 represents noise; reference numeral 302 represents the noise suppression result of only turning on the first active noise reduction filter unit 203 (feed forward, FF); reference numeral 303 represents the noise suppression result of only turning on the second active noise reduction filter unit 204 (feedback, FB); reference numeral 304 represents the expected noise suppression result of turning on the first active noise reduction filter unit 203 and the second active noise reduction filter unit 204 (FF+FB); and reference numeral 305 represents the actual noise suppression result of turning on the first active noise reduction filter unit 203 and the second active noise reduction filter unit 204 (FF+FB). By comparing the reference numerals 304 and 305, it can be observed that the reference numerals 304 and 305 overlap at relatively low frequencies, but do not overlap at relatively high frequencies. In other words, at relatively high frequencies, the actual noise suppression result cannot achieve the expected noise suppression result.

To explain why such a result is obtained, referring back to FIG. 2, d ( n ) represents the main noise signal originating from the external noise signal, i.e., the aforementioned residual noise signal; y1 ( n ₎ represents the first signal related to the first anti-noise signal y'1 ( n ) output _by the first active noise reduction filter unit 203, the first signal y1 ( _n ) being a sound signal; y2 ( n ) represents _the second signal related to the second anti-noise signal y'2 ₍ n ) output by the second active noise reduction filter unit 204, the second signal y2 ( n ) being a sound signal; and e ( n ) represents the error signal output _by the second microphone 202. It should be particularly noted that, in order to simplify the description, the process of converting the sound signal into a digital electrical signal is omitted.

The error signal e ( n ) output by the second microphone 202 can be regarded as an electrical signal in digital form.

When neither of the active noise reduction filter units 203 and 204 is turned on, the second microphone 202 only captures the main noise signal d ( n ) as the error signal e ( n ), that is, e ( n )= d ( n ). When the second active noise reduction filter unit 204 is turned on, the second microphone 202 captures the main noise signal d ( n ) and _the second signal y2 ( n ) as the error signal e ( n ), that is, e ( n )= d ( n )+ y2 ( n ). The main noise signal d ( n ) and the second signal y2 ( n _{) are} added by the adding unit 206. It should be noted that the adding unit 206 shown in the figure is not a physical component, but is only for the convenience of understanding in the analysis. Similarly, when the active noise reduction filter units 203 and 204 are turned on, the second microphone 202 captures the main noise signal d ( n ), _the first signal y1 ( n ) and _the second signal y2 ( n ) as the error signal e ( n ), that is, e ( n ) = d ( n ) + y1 (n ₎ + y2 ( n ₎ .

The second active noise reduction filter unit 204 generates the second anti-noise signal y'2 ( n ) based on the error signal e ( _n ) received by the second microphone 202. However, in this case, based on the formula e ( n )= d ( n )+ y1 ( n )+ y2 ( n ) , it can be _seen that the error signal e ( n ) captured _by the second microphone 202 has been interfered _by the first signal y1 ( n ), so that the second anti-noise signal y'2 ( n ) generated by the second active noise reduction filter unit 204 is not effective, which leads to problems such as excessive _noise processing. In short, each time the sound received by the second microphone 202 contains the first signal y ₁ ( n ), the actual noise cannot be properly suppressed or over-compensated.

The earphone type in the above embodiment is an in-ear earphone, that is, the earphone housing 19 is considered to be able to effectively block _the second signal y2 ( n ) from being transmitted to the outside of the in-ear earphone, so that the first microphone 201 cannot receive _the second signal y2 ( n ). If the earphone is open-type and the earphone housing 19 is considered to be unable to effectively block _the second signal y2 ( n ₎ from being transmitted to the outside of the earphone, the first microphone 201 will receive the second signal y2 ( n ), which will cause the mutual interference to be more serious, and thus may cause the noise to be more serious than the situation with only a single noise reduction system.

To solve the above-mentioned problem, one possible approach is to remove the first signal y ₁ ( n ) from the error signal e ( n ) based on the mathematical principle of linear systems, such as the embodiment of FIG. 4 of the present invention.

FIG. 4 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset with good isolation between the ear canal and the environment according to a preferred embodiment of the present invention. The active noise reduction headset of FIG. 4 adopts a composite noise reduction architecture. Referring to FIG. 4, the active noise reduction headset of FIG. 4 is similar to the active noise reduction headset of FIG. 2, except that the active noise reduction device 20 of FIG. 4 that can stack multiple anti-noise signals further includes a first decoupling unit 40. The first decoupling unit 40 is used to remove the first signal y1 ( n ) in the error signal e ( n ) captured by the second microphone ₂₀₂ by means of electrical signal processing. In some embodiments, the first decoupling unit 40 is implemented by a digital signal processor. In this embodiment, the first path starts from the output of the first microphone 201, passes through the first active noise reduction filter unit 203, and reaches the input of the physical channel 205; and the second path starts from the output of the second microphone 202, passes through the second active noise reduction filter unit 204, and reaches the input of the physical channel 205.

(z)。換言之，模擬的物理通道

(z)實質上相同於物理通道S(z)205。 The first decoupling unit 40 includes a first channel simulation filter 401 and a first adding circuit 402. The first channel simulation filter 401 is, for example, a transfer function of the simulated physical channel 205. The simulated physical channel is represented by a Z-domain transfer function:

( z ). In other words, the simulated physical channel

( z ) is substantially the same as the physical channel S ( z )205.

The physical channel 205 is used to represent the transmission from the active noise reduction filter (e.g., the first active noise reduction filter unit 203 or the second active noise reduction filter unit 204) to the second microphone 202, so as to analyze the conversion of the electrical signal output by the active noise reduction filter after the transmission, wherein the transfer function S ( z ) is used to represent the simulation result. In some possible implementations, the external noise source is removed, and the transfer function S ( z ) is evaluated based on the electrical signal output by the active noise reduction filter and based on the error signal e (n) obtained through the second microphone 202, wherein there is no main noise signal d ( n ) because there is no external noise source. Therefore, the error signal e (n) is substantially the same as at least one _of the first signal y1 ( n ) and the second _signal y2 ( n ) or the sum thereof, depending on the activation status of the first active noise reduction filter unit 203 and the second active noise reduction filter unit 204.

(n)。在模擬的物理通道

(z)實質上相同於物理通道S(z)205的情況下，由於模擬的物理通道

(z)及物理通道S(z)205的輸入訊號均為第一抗噪訊號y'₁(n)，模擬的物理通道

(z)所輸出的第一解耦合訊號

(n)實質上等效於物理通道S(z)205所輸出的第一訊號y ₁(n)。接著，第一加法電路402的第一輸入埠接收第一解耦合訊號

(n)，第一加法電路402的第二輸入埠接收誤差訊號e(n)。接著，第一加法電路402將誤差訊號e(n)中的第一解耦合訊號

(n)的成分扣除(視為扣除第一訊號y ₁(n))，並提供給第二主動降噪濾波單元204。第二主動降噪濾波單元204所接收到的誤差訊號e(n)便實質上等於d(n)+y ₂(n)，不再含有第一訊號y ₁(n)。因此，雜訊抑制效果會顯著的提昇。本實施例藉由第一解耦合單元40在電路的訊號處理中，將誤差訊號e(n)的第一訊號y ₁(n)扣除，以解決上述過度補償的問題。 The first channel analog filter 401 receives the first anti-noise signal y'1 ( n ) output _by the first active noise reduction filter unit 203 to generate a first decoupling signal

( n ). In the simulated physical channel

( z ) is substantially the same as the physical channel S ( z ) 205, since the simulated physical channel

( z ) and the input signal of the physical channel S ( z ) 205 are both the first anti-noise signal y ' ₁ ( n ), and the simulated physical channel

( z ) The first decoupling signal outputted

( n ) is substantially equivalent to the first signal y1 ₍ n ) output by the physical channel S ( z ) 205. Then, the first input port of the first adding circuit 402 receives the first decoupled signal

( n ), the second input port of the first adding circuit 402 receives the error signal e ( n ). Then, the first adding circuit 402 converts the first decoupled signal in the error signal e ( n ) into

The component of y1( n ) is deducted (regarded as deducting _the first signal y1 ( n )) and provided to the second active noise reduction filter unit 204. The error signal e ( n ) received by the second active noise reduction filter unit 204 is substantially equal to d ( n )+ y2 ( _n ) and no longer contains the first signal y1 ( n ). Therefore, the noise suppression effect is significantly improved. In this embodiment, the first decoupling unit 40 deducts the first signal y1 ( _n ) from the error signal e ( n ) in the signal processing of the _circuit to solve the above-mentioned over-compensation problem.

FIG. 5 is a schematic diagram of equivalent sampling time blocks of an active noise reduction headset with good isolation between the ear canal and the environment according to a preferred embodiment of the present invention. The active noise reduction headset of FIG. 5 adopts a composite noise reduction structure. Please refer to FIG. 2 and FIG. 5. In this embodiment, the active noise reduction device 20 capable of stacking multiple anti-noise signals also has an additional first decoupling unit 50 for removing the first signal y ₁ ( n ) by electrical signal processing.

In this embodiment, the first decoupling unit 50 includes a first channel analog filter 501, a third active noise reduction filter unit 502, a first adding circuit 503 and a second adding circuit 504.

(n)，其中，第一抗噪訊號y'₁(n)為由第一麥克風201所接收的外部噪音訊號，並經過取樣數位/類比轉換之後，透過第一主動降噪濾波單元203之運算獲得。 The function of the first channel simulation filter 501 is the same as that of the first channel simulation filter 401 in the embodiment of FIG. 4. The first channel simulation filter 501 is used to simulate the physical channel 205, receive the first anti-noise signal y ' ₁ ( n ), and generate a first decoupled signal

( n ), wherein the first anti-noise signal y'1 ( n ) is _an external noise signal received by the first microphone 201 and is obtained through the operation of the first active noise reduction filter unit 203 after being sampled digital/analog converted.

(n)輸入進第三主動降噪濾波單元502時，第三主動降噪濾波單元502所輸出的第三抗噪訊號可表示為

(n)W ₂。 In this embodiment, the transfer function of the third active noise reduction filter unit 502 is the same as the transfer function of the second active noise reduction filter unit 204, so the weight of the third active noise reduction filter unit 502 is also W ₂ . In other words, the filtering operation of the third active noise reduction filter unit 502 is the same as the filtering operation of the second active noise reduction filter unit 204. Therefore, when the first decoupling signal

( n ) When the signal is input into the third active noise reduction filter unit 502, the third anti-noise signal output by the third active noise reduction filter unit 502 can be expressed as

( n ) W2 _.

The second active noise reduction filter unit 204 receives the error signal output by the second microphone 202, which is labeled as d ( n ) + y ₁ ( n ) + y ₂ ( n ). Therefore, the signal output by the second active noise reduction filter unit 204 is labeled as [ d ( n ) + y ₁ ( n ) + y ₂ ( n )] W ₂ .

(n)W ₂，第一加法 電路503的第二輸入埠接收第二抗噪訊號〔d(n)+y ₁(n)+y ₂(n)〕W ₂。由於

(n)實質上等效於y ₁(n)，因此，第一加法電路503將兩訊號相減之後，輸出近似為〔d(n)+y ₂(n)〕W ₂。此〔d(n)+y ₂(n)〕W ₂即去除了y ₁(n)的成分。又，該輸出〔d(n)+y ₂(n)〕W ₂中的主噪音訊號d(n)可忽略不計。因此，該輸出〔d(n)+y ₂(n)〕W ₂可進一步簡化為式子〔y ₂(n)〕W ₂，其在此表示為y'₂(n)。由此可知，雖然第二主動降噪濾波單元204受到第一訊號y ₁(n)的干擾，但該干擾通過第三主動降噪濾波單元502及第一加法電路503被等效地消除了。 The first input port of the first adding circuit 503 receives the third anti-noise signal

( n ) W ₂ , the second input port of the first adding circuit 503 receives the second anti-noise signal [ d ( n ) + y ₁ ( n ) + y ₂ ( n )] W ₂ .

( n ) is substantially equivalent to y1 ( n ), therefore, after the first adder circuit 503 subtracts the two _signals , the output is approximately _[ d ( n )+ y2 ( n ) _] W2 . This [ d ( n ) +y2(n)]W2 removes the component of y1(n ₎ . _Moreover , the _main noise signal d ₍ n ) in _{the output} [ d ( n )+ y2 ( n )] W2 _can be ignored. Therefore, the output [ d ( n ) + y2 ( n )] W2 can _be further simplified to the formula [ y2 ( n ) _] W2 , which is represented as y'2 ( _n ) here. It can be seen that although the second active noise reduction filter unit 204 is interfered by the first signal y ₁ ( n ), the interference is equivalently eliminated by the third active noise reduction filter unit 502 and the first adding circuit 503 .

The first input port of the second adder circuit 504 is coupled to the output port of the first adder circuit 503 to receive the _output y'2 ( n ). The second input port of the second adder circuit 504 receives the first anti-noise signal y'1 ₍ n ) and adds the two signals to obtain the electrical signal component y'1 ₍ n )+ y'2 ( n ) of the noise _reduction signal. In some embodiments, the second adder circuit 504 can be omitted.

The embodiment of FIG. 5 above adopts a different decoupling method from FIG. 4, but can also eliminate the redundant first signal y ₁ ( n ) component. Another embodiment is proposed below, which can also eliminate the redundant first signal y ₁ ( n ) component, so that those with ordinary knowledge in the relevant technical field can implement the present invention accordingly.

FIG. 6 is a schematic diagram of equivalent sampling time blocks of an active noise reduction headset with good isolation between the ear canal and the environment according to a preferred embodiment of the present invention. The active noise reduction headset of FIG. 6 adopts a composite noise reduction architecture. Unlike the embodiment of FIG. 5, which processes the error signal e ( n ) provided by the second microphone 202 to achieve the decoupling effect, in the embodiment of FIG. 6, the signal provided by the first microphone 201 is processed to achieve the decoupling effect, as described in detail below.

The first decoupling unit 60 includes a third active noise reduction filter unit 601, a channel simulation filter 602, a first adding circuit 603 and a second adding circuit 604, wherein the function of the channel simulation filter 602 is the same as the first channel simulation filter 401 of the embodiment of FIG. 4.

(n)W ₂。 The operation of the third active noise reduction filter unit 601 is the same as that of the second active noise reduction filter unit 204. The difference is that the third active noise reduction filter unit 601 receives the first anti-noise signal y ' ₁ ( n ) output by the first active noise reduction filter unit 203 and outputs a third anti-noise signal y ' ₁ ( n ) W ₂ . After that, it is processed by the channel simulation filter 602 to generate a first decoupling signal

( n ) W2 _.

In addition, the operation of the third active noise reduction filter unit 601 is similar to the third active noise reduction filter unit 502 in FIG. 5, except that in the embodiment of FIG. 5, the first anti-noise signal y'1 ( n ) is first processed _by the first channel simulation filter 501 and then processed by the third active noise reduction filter unit 502, while in the present embodiment, the first anti-noise signal y'1 ( n ) is first processed by the third active noise reduction filter unit 601 and then processed by the channel simulation filter 602. According to the mathematical principles of linear systems, the difference in _the above configuration order does not substantially lead to a change in the result, which will not be elaborated here. Accordingly, in some embodiments, it can be configured that the first anti-noise signal y ' ₁ ( n ) is first processed by the channel simulation filter 602 and then processed by the third active noise reduction filter unit 601.

(n)W ₂，第一加法電路603的第二輸入埠接收第一抗噪訊號y'₁(n)，並將兩者相減，之後透過第二加法電路604將第二主動降噪濾波單元204路徑上的訊號進行互相干涉，以消除第二主動降噪濾波單元204輸出的抗噪訊號〔d(n)+y ₁(n)+y ₂(n)〕W ₂中多餘的第一訊號y ₁(n)成分。明確來說，第一加法電路603輸出的訊號[y'₁(n)-

(n)W ₂]中的成分

(n)W ₂用來消除第二主動降噪濾波單元204輸出的抗噪訊號〔d(n)+y ₁(n)+y ₂(n)〕W ₂中的成分[y ₁(n)W ₂]。又，抗噪訊號〔d(n)+y ₁(n)+y ₂(n)〕W ₂中的主噪音訊號d(n)可忽略不計。據此，第二加法電路604輸出的訊號為[y ₂(n)W ₂+y'₁(n)]，其進一步 簡化為[y'₂(n)+y'₁(n)]。 The first input port of the first adding circuit 603 receives the first decoupling signal

( n ) W ₂ , the second input port of the first adding circuit 603 receives the first anti-noise signal y ' ₁ ( n ) and subtracts the two. Then, the second adding circuit 604 interferes with the signals on the path of the second active noise reduction filter unit 204 to eliminate the redundant first signal y ₁ ( n ) component in the anti-noise signal [ d ( n ) + y ₁ ( n ) + y ₂ ( n )] W ₂ output by the second active noise reduction filter unit 204. Specifically, the signal [ y ' ₁ ( n ) -

( n ) W ₂ ]

( n ) W2 is used to eliminate the component [ y1 _{( n} ) W2 ] in _the anti-noise signal [ d ( n )+ y1 ( n )+ y2 (n ) _] W2 output by the _second active noise reduction filter unit _204. In addition, the main noise signal d ( n ) in _the anti-noise signal [ d ( n _{) +} y1 ( n )+ y2 ( n ) _] W2 can be ignored. Accordingly, the signal output by the second adder circuit 604 _{is [y2(n)W2 +} y'1 ( n ) ] , which is _further simplified to [ y'2 (n ₎ + y'1 ( n )].

In the above embodiments, in-ear headphones are used as examples. Since in-ear headphones have good isolation between the internal microphone and the external microphone, the noise received by the internal microphone cannot be received by the external microphone. Therefore, in the above embodiments, the echo noise cannot affect the first microphone 201. The following is an example without good isolation.

FIG. 7 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset without good isolation between the ear canal and the environment in a preferred embodiment of the present invention. The active noise reduction headset in FIG. 7 adopts a composite noise reduction structure. Please refer to FIG. 7. In this embodiment, the active noise reduction headset is semi-in-ear. The headset housing 19 of this type of active noise reduction headset cannot effectively block the sound from being transmitted from the inside of the active noise reduction headset to the outside of the active noise reduction headset, so the reverse noise of the internal echo of the ear canal will also interfere with the first microphone 201 located outside the headset. Therefore, the active noise reduction device of the system of the above-mentioned active noise reduction headset that can stack multiple anti-noise signals includes a second decoupling unit 70 in addition to the first decoupling unit 40.

This technology has the same concept as the above-mentioned embodiments. The first decoupling unit 40 is used to generate a first decoupling signal according to the anti-noise signal output by the first active noise reduction filter unit 203. Similarly, the second decoupling unit 70 is used to generate a second decoupling signal according to the anti-noise signal output by the second active noise reduction filter unit 204.

(n)，此第一解耦合訊號

(n)實質上幾乎等於第一訊號y ₁(n)。第二麥克風202所接收的第一誤差訊號e ₂(n)為[d ₂(n)+y ₁(n)+y ₂(n)]。接著，第一加法電路402的第一輸入埠接收第一解耦合訊號

(n)，第一加法電路402的第二輸入埠接收第一誤差訊號e ₂(n)。藉此，第一解耦合訊號

(n)將第一誤差訊號e ₂(n)的y ₁(n)成分扣除，並輸出給第二主動降噪濾波單元204，第二主動降噪濾波單元204所接收到的訊號e ₂’(n)便實質上等於d ₂(n)+y ₂(n)。換言之，第二主動降噪濾波單元204不再受到第一訊號y ₁(n)的干擾，而能夠產生有效的抗噪訊號。為了方便說明第7圖的實施例中，物理通道205的轉移函數表示為S ₁(z)，第一通道模擬濾波器401的轉移函數表示為

(z)。 In this embodiment, the first decoupling unit 40 is similar to the embodiment of FIG. 4 and includes a first channel analog filter 401 and a first adding circuit 402. The first channel analog filter 401 is substantially the same as the physical channel 205, and receives _the first anti-noise signal y'1 ( n ) output by the first active noise reduction filter unit 203 to generate a first decoupling signal

( n ), the first decoupling signal

( n ) is substantially equal to _the first signal y1 ( n ). The first error signal e2 ( n ) received by the second microphone 202 is [d2 _{( n} ) + y1 ( n )+ y2 ( n ) _] . Then, the first input port _of the first adder circuit 402 receives the first decoupled signal

( n ), the second input port of the first adding circuit 402 receives _the first error signal e2 ( n ). Thus, the first decoupled signal

( n ) deducts the y1 ( _n ) component _of the first error signal e2 ( n ) and outputs it to the second active noise reduction filter unit 204. The signal e2 '( n ₎ received by the second active noise reduction filter unit 204 is substantially equal _to d2 ( n )+ y2 ( n ₎ . In other words, the second active noise reduction filter unit 204 is no longer interfered by the first signal y1 ( n ) and can generate an effective anti-noise signal. For the convenience of explaining the embodiment of FIG. 7, the transfer function of the physical channel 205 is represented _by S1 ( z ), _and the transfer function of the first channel analog filter 401 is represented by

( z ).

On the other hand, since the appearance of the earphone in this embodiment is not isolated, the reverse noise of the internal echo of the ear canal will also interfere with the external first microphone 201. The other physical channel 72 of the real environment is also represented by the Z-domain transfer function as S2 ( z ). In other words, the transfer function S2 ( z ) _of the second physical channel ₇₂ is used to represent the transmission between the active noise reduction integrated circuit 20 and the input of the first microphone 201. Similarly, after the anti-noise signals y ' ₁ ( n ) and y ' ₂ ( n ) output by the active noise reduction device 20 capable of stacking multiple anti-noise signals are transmitted through the second physical channel 72, x ₁ ( n ) represents the sound signal corresponding to the first anti-noise signal y ' ₁ ( n ), and x ₂ ( n ) represents the sound signal corresponding to the second anti-noise signal y ' ₂ ( n ). In terms of actual sound signal transmission, since the signals x ₁ ( n ) and x ₂ ( n ) are transmitted from the ear canal to the first microphone 201, their channel response is different from the channel response in the ear canal. Therefore, the signals x ₁ ( n ) and x ₂ ( n ) are different from the sound signals y ₁ ( n ) and y ₂ ( n ).

In addition to receiving signals x1 ( _n ) and x2 ( n ₎ , the first microphone 201 also receives _an external noise _signal d1 ( n ). Accordingly, the first microphone 201 uses _the external noise signal d1 ( n ), signals x1 ( n ) and x2 ( n ) as a second error signal e1 ( n ₎ . In addition, the external noise signal d1 ( _n ) enters the active noise canceling headset from the outside and is converted into a main noise signal d2 ( _n ). _The main noise signal d2 ( n ) is substantially equivalent to _the main noise signal d ( n ) of the embodiment of FIG. 2.

If _the second error signal e1 (n) is not processed and the first active noise reduction filter unit 203 receives _the second error signal _e1 ( n ) including the signal x2 (n) , similar to the reason described in the embodiment of FIG. 2, the first active noise reduction filter unit 203 is interfered by _the signal x2 ( n ), and the anti-noise signal generated thereby cannot effectively eliminate the noise. Therefore, _the signal _x2 ( n) needs to be removed from the second error signal e1 ( n ) so that the signal received by the first active noise reduction filter unit 203 does not contain the signal x2 (n ₎ .

Therefore, the present embodiment proposes a second decoupling unit 70, including a second channel simulation filter 701 and a second adding circuit 702. Since _the signal x2 ( n ) is output by the physical channel 72, in order to effectively eliminate the signal _x2 ( n ) in the second _error signal e1 ( n ), the second channel simulation filter 701 needs to simulate the physical channel 72 instead of simulating the physical channel 205.

(n)。此第二解耦合訊號

(n)實質上幾乎等於訊號x ₂(n)。接著，第二加法電路702的第一輸入埠接收第二解耦合訊號

(n)，第二加法電路702的第二輸入埠接收第二誤差訊號e ₁(n)。藉此，將第二誤差訊號e ₁(n)中的訊號x ₂(n)成分扣除，並輸出給第一主動降噪濾波單元203。第一主動降噪濾波單元203所接收到的訊號e ₁’(n)便實質上等於d ₁(n)+x ₁(n)，第一主動降噪濾波單元203不會受到訊號x ₂(n)的干擾，因而產生的第一抗噪訊號y'₁(n)是有效的。 The second channel analog filter 701 receives the second anti-noise signal y'2 ( n ) output _by the second active noise reduction filter unit 204 to generate a second decoupling signal

( n ). The second decoupled signal

( n ) is substantially equal to _the signal x2 ( n ). Then, the first input port of the second adding circuit 702 receives the second decoupled signal

( n ), the second input port of the second adding circuit 702 receives _the second error signal e1 ( n ). Thus, _the signal x2 ( n ) component in the second error _signal e1 ( n ) is subtracted and output to the first active noise reduction filter unit 203. The signal e1 _' ( n ) received by the first active noise reduction filter unit 203 is substantially equal _to d1 ( n )+ x1 ( n ) _. The first active noise reduction filter unit 203 will not be interfered by _the signal x2 ( n ), so _the generated first anti-noise signal y'1 ( n ) is effective.

In this embodiment, the first path starts from the output end of the first microphone 201, passes through the first active noise reduction filter unit 203, and reaches the input ends of the physical channels 205 and 72. The second path starts from the output end of the second microphone 202, passes through the second active noise reduction filter unit 204, and reaches the input ends of the physical channels 205 and 72. The first path anti-noise signal is converted into _a third signal x1 ( n ) by the second physical channel 72. The second path anti-noise signal is converted into _a fourth signal x2 ( n ) by the second physical channel 72. In other words, the first path receives _the second error signal e1 ( n ) containing _the fourth signal x2 ( n ) component, so that the first active noise reduction filter unit 203 in the first path is interfered by the _fourth signal x2 ( n ). The second decoupling unit 70 in this embodiment removes the component of the fourth signal x ₂ ( n ) in the first path based on the second anti-noise signal y ' ₂ ( n ).

In other embodiments, only a single microphone is used for implementation, but there are examples of dual anti-noise systems. As shown in FIG. 8, FIG. 8 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset of a preferred embodiment of the present invention. The active noise reduction headset of the embodiment of FIG. 8 adopts a feedback noise reduction architecture. Please refer to FIG. 8. In this embodiment, there is only a second microphone 202 (in-ear canal noise receiving microphone), however, in this embodiment, there is a first active noise reduction filter unit 203 and a second active noise reduction filter unit 204.

(n)。同樣地，第二加法電路802接收第二解耦合訊號

(n)與誤差訊號e(n)，並將誤差訊號e(n)中的訊號y ₂(n)成分扣除，輸出給第一主動降噪濾波單元203。第一主動降噪濾波單元203所接收到的訊號e ₁’(n)便實質上等於d(n)+y ₁(n)，使得第一主動降噪濾波單元203不會受到訊號y ₂(n)的干擾，因而產生有效噪的第一抗噪訊號y'₁(n)。 Different from the embodiment of FIG. 7 , if the signal received by the first active noise reduction filter unit 203 is not decoupled, that is, the first active noise reduction filter unit 203 directly receives the error signal e ( n ) that has not _been decoupled, the first active noise reduction filter unit 203 will be interfered by _the second signal y2 ( n ) instead of the signal x2 ( n ) of the embodiment of FIG. 7 . Therefore, in order to effectively eliminate the signal y2 ( n ) in the error signal e ( n ), the channel simulation filter 801 in the second decoupling unit 80 needs to simulate the above-mentioned physical channel 205 instead of simulating the physical channel 72 to generate _the second decoupled signal

( n ). Similarly, the second adding circuit 802 receives the second decoupling signal

( n ) and the error signal e ( n ), and deducts the signal y2 ( _n ) component in the error signal e ( n ), and outputs it to the first active noise reduction filter unit 203. The signal e1 '( _n ) received by the first active noise reduction filter unit 203 is substantially equal to d (n ) + y1 ( n ), so that the first active noise reduction filter unit 203 will not be interfered _{by the} signal y2 ( n ), thereby generating the first anti-noise signal y'1 ( n ) _with effective noise.

That is, please refer to Figure 7 and Figure 8. The embodiments of Figure 7 and Figure 8 adopt almost the same elimination structure. The only difference is that Figure 8 only has the second microphone 202. Since the method of eliminating redundant components is similar, it will not be elaborated here.

In this embodiment, the first path starts from the output of the second microphone 202, passes through the first active noise reduction filter unit 203, and reaches the input of the physical channel 205. The second path starts from the output of the second microphone 202, passes through the second active noise reduction filter unit 204, and reaches the input of the physical channel 205.

FIG. 9 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset with good isolation between the ear canal and the environment in a preferred embodiment of the present invention. The active noise reduction headset in FIG. 9 adopts a composite noise reduction structure. Please refer to FIG. 9 and FIG. 8 first. The difference between FIG. 9 and FIG. 8 is that the feedforward noise reduction is additionally added, that is, the first microphone 201 and the third active noise reduction filter unit 91 are added.

For the first active noise reduction filter unit 203, if the signal received by the first active noise reduction filter unit 203 is not decoupled, the first active noise reduction filter unit 203 will be interfered by the signals y0 ₍ n ) and y2 ( _n ). Therefore, the channel simulation filter 901 and the adder circuit 902 in the third decoupling unit 90 are used to eliminate the _interference of the signal y0 ( n ), and the second decoupling unit 80 is used to eliminate the interference of the signal y2 ₍ n ). The principle of eliminating interference is the same as that of the aforementioned embodiments, and will not be repeated here.

For the second active noise reduction filter unit 204, if the signal received by the second active noise reduction filter unit 204 is not decoupled, the second active noise reduction filter unit 204 will be interfered by the signals y0 ₍ n ) and y1 ( _n ). Therefore, the channel simulation filter 901 and the adder circuit 903 in the third decoupling unit 90 are used to eliminate the _interference of the signal y0 ( n ), and the first decoupling unit 40 is used to eliminate the interference of the signal y1 (n ₎ . The principle of eliminating interference is the same as that of the aforementioned embodiments, and will not be repeated here. In addition, in the present embodiment, in order to simplify the wiring complexity in the component schematic diagram, the relative positions of the adding unit 206 and the second microphone 202 in FIG. 9 are swapped with the positions of the adding unit 206 and the second microphone 202 in FIG. 8 . However, a person having ordinary skill in the art should be able to infer that the relative positions of the adding unit 206 and the second microphone 202 in the diagram cannot be used to limit the component configuration of the present invention.

As can be seen from the above description, the present embodiment further includes a third path, which starts from the output end of the first microphone 201, passes through the third active noise reduction filter unit 91, and reaches the input end of the physical channel 205. _The third anti-noise signal y'0 ( n ) output by the third active noise reduction filter unit 91 is, for example, a third path anti-noise signal in the present embodiment, and the third anti-noise signal y'0 ₍ n ) is converted into the _third signal y0 ( n ) through the physical channel 205. Since both the first path and the second path receive _the error signal e ( n ) containing the third signal y0 ( n ) component. Therefore, the third decoupling unit 90 proposed in this embodiment removes the components of the third signal y ₀ ( n ) in the first path and the second path based on the third anti-noise signal y ' ₀ ( n ).

In order to solve the above-mentioned problems, the embodiment of the present invention proposes an active noise reduction method that can stack multiple anti-noise signals. FIG. 10 is a flow chart of an active noise reduction method that can stack multiple anti-noise signals of a preferred embodiment of the present invention. Please refer to FIG. 10. This active noise reduction method that can stack multiple anti-noise signals includes the following steps:

Step S1001: Provide a first path, output a first path anti-noise signal, wherein the first path anti-noise signal is converted into a first signal by a physical channel, and the first path includes: a first active noise reduction filter unit, used to generate a first anti-noise signal; provide a second path, receive an error signal containing a component of the first signal, and output a second path anti-noise signal to the physical channel, the second path includes: a second active noise reduction filter unit, used to generate a second anti-noise signal, wherein the second anti-noise signal derives the second path anti-noise signal.

Step S1002: Based on the first anti-noise signal, remove the component of the first signal in the second path. As shown in FIG. 4, by passing the first anti-noise signal through the first channel analog filter 401, at the input end of the second active noise reduction filter unit, the component of the first signal y1 ( n ) in the error signal e ( n ) to be received by the second active noise reduction filter unit 204 is removed. Furthermore, as shown in FIG. ₅ , by passing the first anti-noise signal through the first channel analog filter 501 and the third active noise reduction filter unit 502 (this unit has the same transfer function as the second active noise reduction filter unit), a decoupling signal is generated, and decoupling is performed at the output end of the second active noise reduction filter unit 204. Similarly, as shown in FIG. 6 , the first anti-noise signal is passed through the sound channel simulation filter 602 and the third active noise reduction filter unit 601 (this unit has the same transfer function as the second active noise reduction filter unit) to generate a decoupling signal, and the decoupling is performed after the output of the second active noise reduction filter unit 204. In other words, as long as there are at least two active noise reduction filter units and the anti-noise signals generated by the above active noise reduction filter units are coupled to each other, the decoupling signal can be generated by one of the specific anti-noise signals to eliminate the components of the specific anti-noise signal in the path of other active noise reduction filter units. In this way, the present invention can eliminate the above mutual interference. The embodiments of Figures 7, 8 and 9 are derived from this spirit. Therefore, the present invention is not limited to Figures 4, 5 and 6.

Step S1003: Playing based on the first path anti-noise signal and the second path anti-noise signal to eliminate noise.

In summary, the spirit of the present invention is to set up multiple active noise reduction filter units in the active noise reduction device in the active noise reduction headset, and the output signal of each active noise reduction filter unit causes the redundant components generated by other active noise reduction filter units, and the above redundant components are eliminated by decoupling. Therefore, the signals output by the above multiple active noise reduction filter units can be properly stacked in accordance with the situation of real noise, and the output noise reduction signal can better conform to the received noise and can more properly eliminate the noise.

In the above embodiment, the filter circuit located on the first path in the active noise reduction integrated circuit 20 is used for the purpose of active noise reduction. However, this is only an example and is not a limitation of the present invention. In fact, any application using the decoupling technology proposed by the present invention falls within the scope of the present invention.

In one example, an active noise reduction integrated circuit using the decoupling technology proposed by the present invention can have an active noise reduction function (e.g., feedback noise reduction function) integrated with a hearing aid (HA) function. The principle of HA is to amplify the sound captured by the reference microphone and then play it to the hearing-impaired user to compensate for hearing loss. The audio amplification characteristics are controlled by the HA filter (which is a non-active noise reduction filter).

In another example, an active noise reduction integrated circuit using the decoupling technology proposed in the present invention can have an active noise reduction function (e.g., a feedback noise reduction function) integrated with a pass-through (hereinafter referred to as PT) function. PT is very similar to HA and is used to correct the sound captured by the reference microphone and then play it to the user to restore the sound blocked or attenuated by the outer casing of the earmuffs/in-ear headphones. In some applications, the PT function can be used to enhance the audio components in the high-frequency band that are blocked or attenuated by the outer casing of the earmuffs/in-ear headphones, so that the user wearing the earmuffs/in-ear headphones operating in the PT mode can hear the ambient sound that is very similar to the ambient sound heard by the user who does not wear the earmuffs/in-ear headphones. Audio compensation is controlled by a PT filter (which is a non-active noise reduction filter).

In yet another example, an active noise reduction integrated circuit using the decoupling technology proposed in the present invention can have an active noise reduction function (e.g., a feedback noise reduction function) integrated with a personal sound amplification (PSAP) function. As the name implies, PSAP is only used to amplify sound and does not address other audio components of hearing loss. Specifically, PSAP has not been approved as a medical device by the U.S. Food and Drug Administration (FDA) and is classified as a wearable electronic product for occasional entertainment use by users with normal hearing. The audio amplification characteristics are controlled by the PSAP filter (which is a non-active noise reduction filter).

Active noise reduction (e.g., feedback noise reduction) can eliminate low-frequency noise picked up by the in-ear microphone used as an error microphone and help reduce the occlusion effect caused by the HA/PT/PSAP. However, active noise reduction (e.g., feedback noise reduction) also eliminates the sound played by the speakers of the over-ear headphones/in-ear headphones, thereby reducing the performance of the HA/PT/PSAP. The above-mentioned decoupling technology can also be used to improve the performance of the HA/PT/PSAP provided by a non-active noise reduction filter by reducing or eliminating the side effects caused by the active noise reduction filter (e.g., feedback noise reduction filter).

FIG11 is a schematic diagram of equivalent sampling time blocks of an active noise reduction headphone with good isolation between the ear canal and the environment according to a preferred embodiment of the present invention. The active noise reduction headphone shown in FIG11 is similar to the active noise reduction headphone shown in FIG4, but the difference between the two is that the active noise reduction integrated circuit 110 is used to stack at least one anti-noise signal and at least one non-anti-noise signal, and includes a non-active noise reduction filter unit (e.g., digital filter) 1103 replacing the first active noise reduction filter unit 203 (e.g., digital filter) shown in FIG4. Therefore, the first decoupling unit 40 receives the non-anti-noise signal y'1 ( n ) output from the non-active noise reduction filter unit 1103, instead of the first anti-noise signal _y'1 (n) output from the first active noise reduction filter unit 203, and is used to remove the first signal _y1 ( n ) in the error signal e ( n ) captured by the second microphone ₂₀₂ by means of electrical signal processing . In this embodiment, the first path starts from the output end of the first microphone 201, through the non-active noise reduction filter unit 1103, to the input end of the physical channel 205; and the second path starts from the output end of the second microphone 202, through the second active noise reduction filter unit 204, to the input end of the physical channel 205. Since the first signal y ₁ ( n ) (which is derived by transmitting the non-noise-resistant signal y ' ₁ ( n ) via the physical channel 205) is removed from the second path via the first decoupling unit 40, the side effects brought about by the second active noise reduction filter unit 204 can be reduced or eliminated to achieve the intended purpose of the non-active noise reduction filter unit 1103, that is, feedback noise reduction will not cause the loss of the first signal y ₁ ( n ), and the intended purpose of the non-active noise reduction filter unit 1103 can be achieved without reducing performance.

The present invention does not limit the implementation of the non-active noise reduction filter unit 1103. The non-active noise reduction filter unit 1103 can be set by any suitable non-active noise reduction filter required by the actual application. For example, the non-active noise reduction filter unit 1103 can be a HA filter with a weight marked as W _HA . For another example, the non-active noise reduction filter unit 1103 can be a PT filter with a weight marked as W _PT . For another example, the non-active noise reduction filter unit 1103 can be a PSAP filter with a weight marked as W _PSAP .

Except for the generation _of the filter output y'1 ( n ), the active noise reduction integrated circuit 110 shown in FIG. 11 has the same circuit architecture as the active noise reduction integrated circuit 20 shown in FIG. 4. Since those skilled in the art can easily understand the mathematical principles of the active noise reduction integrated circuit 110 shown in FIG. 11 after reading the above paragraphs on the active noise reduction integrated circuit 20 shown in FIG. 4, for the sake of brevity, further description is omitted here.

(n)，其中，非抗噪訊號y'₁(n)的產生方式為由第一麥克風201所接收的外部噪音訊號，並經過取樣及數位/類比轉換之後，透過非主動降噪濾波單元1103之運算獲得。再者，第二加法電路504的第二輸入埠是接收非主動降噪濾波單元1103所輸出的非抗噪訊號y'₁(n)，而非接收第一主動降噪濾波單元203輸出的第一抗噪訊號y' ₁(n)。 FIG. 12 is a schematic diagram of equivalent sampling time blocks of an active noise reduction headphone with good isolation between the ear canal and the environment according to a preferred embodiment of the present invention. The active noise reduction headphone of FIG. 12 is similar to the active noise reduction headphone shown in FIG. 5 , but the difference between the two is that the active noise reduction integrated circuit 110 is used to stack at least one anti-noise signal and at least one non-anti-noise signal, and includes a non-active noise reduction filter unit 1103 that replaces the first active noise reduction filter unit 203 shown in FIG. 5 . Therefore, in this embodiment, the first decoupling unit 50 receives the non-anti-noise signal y' ₁ ( n ) output from the non-active noise reduction filter unit 1103 instead of the first anti-noise signal y' ₁ ( n ) output from the first active noise reduction filter unit 203. Specifically, the first channel simulation filter 501 is used to simulate the physical channel 205 and receive _the non-anti-noise signal y'1 ( n ) to generate the first decoupled signal

( n ), wherein the non-anti-noise signal y'1 ( n ) is generated by the external noise signal received by the first microphone 201, and after sampling and digital/analog conversion, it is obtained by the operation _of the non-active noise reduction filter unit 1103. Furthermore, the second input port of the second adding circuit 504 receives _the non-anti-noise signal y'1 ( n ) output by the non-active noise reduction filter unit 1103, instead of receiving the first anti-noise signal y'1 ( n ) output _by the first active noise reduction filter unit 203.

It can be seen that although the second active noise reduction filtering unit 204 is interfered by the first signal y ₁ ( n ), this interference is equivalently eliminated by the third active noise reduction filtering unit 502 and the first adding circuit 503 . Since the first signal y ₁ ( n ) (which is derived by transmitting the non-noise-resistant signal y' ₁ ( n ) via the physical channel 205) is removed from the second path via the first decoupling unit 50, the side effects brought about by the second active noise reduction filter unit 204 can be reduced or eliminated to achieve the intended purpose of the non-active noise reduction filter unit 1103, that is, feedback noise reduction will not cause the loss of the first signal y ₁ ( n ), and the intended purpose of the non-active noise reduction filter unit 1103 can be achieved without reducing performance.

The present invention does not limit the implementation of the non-active noise reduction filter unit 1103. The non-active noise reduction filter unit 1103 can be set by any suitable non-active noise reduction filter required by the actual application. For example, the non-active noise reduction filter unit 1103 can be a HA filter with a weight marked as W _HA . For another example, the non-active noise reduction filter unit 1103 can be a PT filter with a weight marked as W _PT . For another example, the non-active noise reduction filter unit 1103 can be a PSAP filter with a weight marked as W _PSAP .

According to the mathematical principles of linear systems, the difference in configuration order will not cause the result to change. For example, in some embodiments, the non-anti-noise signal y ' ₁ ( n ) output by the non-active noise reduction filter unit 1103 can be configured to be processed by the third active noise reduction filter unit 502 first, and then processed by the first channel analog filter 501.

Except for the generation _of the filter output y'1 ( n ), the active noise reduction integrated circuit 110 shown in FIG. 12 has the same circuit architecture as the active noise reduction integrated circuit 20 shown in FIG. 5. Since those skilled in the art can easily understand the mathematical principles of the active noise reduction integrated circuit 110 shown in FIG. 12 after reading the above paragraphs on the active noise reduction integrated circuit 20 shown in FIG. 5, for the sake of brevity, further description is omitted here.

The embodiment of FIG. 12 adopts a different decoupling method from the embodiment of FIG. 11, but can also eliminate the redundant first signal y ₁ ( n ) component. Another embodiment is proposed below, which can also eliminate the redundant first signal y ₁ ( n ) component, so that those with ordinary knowledge in the relevant technical field can implement the present invention accordingly.

FIG13 is a schematic diagram of equivalent sampling time blocks of an active noise reduction headphone with good isolation between the ear canal and the environment according to a preferred embodiment of the present invention. The active noise reduction headphone of FIG13 is similar to the active noise reduction headphone shown in FIG6 , but the difference between the two is that the active noise reduction integrated circuit 110 is used to stack at least one anti-noise signal and at least one non-anti-noise signal, and includes a non-active noise reduction filter unit 1103 replacing the first active noise reduction filter unit 203 shown in FIG6 . In the embodiment shown in FIG. 13 , the signal provided by the first microphone 201 is processed to achieve a decoupling effect, so that the first decoupling unit 60 receives the non-anti-noise signal y ' ₁ ( n ) output from the non-active noise reduction filter unit 1103, instead of the first anti-noise signal y ' 1 ( n ) output from the first active noise reduction filter unit 203. Specifically, the third active noise reduction filter unit 601 receives the non-anti-noise signal y _{' 1} ( n ) _output from the non-active noise reduction filter unit 1103, and outputs the third anti-noise signal y ' ₁ ( n ) W ₂ . In addition, the second input port of the first adding circuit 603 receives the non-anti-noise signal y'1 ( n ) output _by the non-active noise reduction filter unit 1103, instead of the first anti-noise signal y'1 ( n ) output by the first active noise reduction filter unit ₂₀₃ .

In addition, the operation of the third active noise reduction filter unit 601 is similar to the operation of the third active noise reduction filter unit 502 shown in FIG. 12, and the difference between the two is that the non-anti-noise signal y ' ₁ ( n ) in the embodiment of FIG. 12 is first processed by the first channel simulation filter 501 and then processed by the third active noise reduction filter unit 502, however, in this embodiment, the non-anti-noise signal y ' ₁ ( n ) is first processed by the third active noise reduction filter unit 601 and then processed by the channel simulation filter 602. According to the mathematical principles of linear systems, the difference in the above configuration order will basically not lead to a change in the result, and the detailed description is omitted here. Therefore, in some embodiments, the non-anti-noise signal y ' ₁ ( n ) may also be configured to be first processed by the channel simulation filter 602 and then processed by the third active noise reduction filter unit 601.

(n)W ₂，第一加法電路603的第二輸入埠接收非抗噪訊號y'₁(n)，且兩個訊號之一者會自該兩個訊號之另一者中減去，然後，透過第二加法電路604讓相減後的訊號與第二主動降噪濾波單元204所在路徑上的訊號彼此干擾，來從第二主動降噪濾波單元204所輸出的抗噪訊號[d(n)+y ₁(n)+y ₂(n)]W ₂中消除第一訊號y ₁(n)的成分。明確來說，第一加法電路603所輸出之訊號[y'₁(n)-

(n)W ₂]中的成分

(n)W ₂會用來消除第二主動降噪濾波單元204所輸出之抗噪訊號[d(n)+y ₁(n)+y ₂(n)]W ₂中的成分[y ₁(n)W ₂]。此外，抗噪訊號[d(n)+y ₁(n)+y ₂(n)]W ₂中的主要雜訊訊號d(n)可以忽略，因此，第二加法電路604輸出的訊號為[y ₂(n)W ₂+y'₁(n)]，其可以再簡化為[y ₂(n)+y'₁(n)]。由於 第一訊號y ₁(n)(其是經由物理通道205傳送非抗噪訊號y' ₁(n)來衍生得到)會透過第一解耦合單元60而從第二路徑移除，故可以減輕或消除第二主動降噪濾波單元204所帶來的副作用而實現非主動降噪濾波單元1103的預期目的，亦即，反饋式降噪不會導致第一訊號y ₁(n)的損失，並且可以在不降低性能的情況下實現非主動降噪濾波單元1103的預期目的。 The first input port of the first adding circuit 603 receives the first decoupling signal

( n ) W ₂ , the second input port of the first adder circuit 603 receives the non-anti-noise signal y ' ₁ ( n ), and one of the two signals is subtracted from the other of the two signals. Then, the subtracted signal is interfered with the signal on the path of the second active noise reduction filter unit 204 by the second adder circuit 604, so as to eliminate the component of the first signal y ₁ ( n ) from the anti-noise signal [ d ( n ) + y ₁ ( n ) + y ₂ ( n )] W ₂ output by the second active noise reduction filter unit 204. Specifically, the signal [ y ' ₁ ( n ) -

( n ) W ₂ ]

( n ) W2 is used to eliminate the component [ y1 ( _n )W2 _{] in the} anti-noise signal [ d ( n )+ y1 ( _n )+ y2 ( n )] W2 output by the second active noise reduction filter unit 204. In addition, _the main noise signal d ( _n ) in _the anti-noise signal [ d ( n _{) +} y1 ( n )+ y2 ( n )] W2 can be ignored . Therefore, the signal output by the second adder circuit 604 _is [ y2 ( n ) W2 + y'1 ( n )], which can _be further simplified to _[ y2 (n ₎ + y'1 ( n )]. Since the first signal y ₁ ( n ) (which is derived by transmitting the non-noise-resistant signal y' ₁ ( n ) via the physical channel 205) is removed from the second path via the first decoupling unit 60, the side effects brought about by the second active noise reduction filter unit 204 can be reduced or eliminated to achieve the intended purpose of the non-active noise reduction filter unit 1103, that is, feedback noise reduction will not cause the loss of the first signal y ₁ ( n ), and the intended purpose of the non-active noise reduction filter unit 1103 can be achieved without reducing performance.

The present invention does not limit the implementation of the non-active noise reduction filter unit 1103. The non-active noise reduction filter unit 1103 can be set by any suitable non-active noise reduction filter required by the actual application. For example, the non-active noise reduction filter unit 1103 can be a HA filter with a weight marked as W _HA . For another example, the non-active noise reduction filter unit 1103 can be a PT filter with a weight marked as W _PT . For another example, the non-active noise reduction filter unit 1103 can be a PSAP filter with a weight marked as W _PSAP .

Except for the generation _of the filter output y'1 ( n ), the active noise reduction integrated circuit 110 shown in FIG. 13 has the same circuit architecture as the active noise reduction integrated circuit 20 shown in FIG. 6. Since those skilled in the art can easily understand the mathematical principles of the active noise reduction integrated circuit 110 shown in FIG. 13 after reading the above paragraphs on the active noise reduction integrated circuit 20 shown in FIG. 6, for the sake of brevity, further description is omitted here.

In the above embodiments, in-ear headphones are used as examples. Since in-ear headphones have good isolation between the internal microphone and the external microphone, the external microphone cannot receive the noise received by the internal microphone. Therefore, in the above embodiments, the echo noise cannot affect the first microphone. The following is an example without good isolation.

FIG. 14 is a schematic diagram of an equivalent sampling time block of an active noise reduction headset without good isolation between the ear canal and the environment, which is a preferred embodiment of the present invention. The active noise reduction headset shown in FIG. 14 is similar to the active noise reduction headset shown in FIG. 7, and the difference between the two is that the active noise reduction integrated circuit 110 is used to stack at least one anti-noise signal and at least one non-anti-noise signal, and includes a non-active noise reduction filter unit 1103 that replaces the first active noise reduction filter unit 203 shown in FIG. 7.

Referring to FIG. 14, in this embodiment, the active noise reduction earphone is a semi-in-ear earphone. Since the earphone housing 19 of such active noise reduction earphone cannot effectively prevent the sound from being transmitted from the inside of the active noise reduction earphone to the outside of the active noise reduction earphone, the first microphone 201 disposed outside the earphone will be disturbed by the echo noise from the inside of the ear canal. Therefore, in addition to the first decoupling unit 40, the above-mentioned active noise reduction earphone system further includes a second decoupling unit 70, which has a function similar to that of the first decoupling unit 40.

This embodiment has the same concept as the aforementioned embodiments. The first decoupling unit 40 is used to generate a first decoupling signal according to the non-anti-noise signal output by the non-active noise reduction filter unit 1103. Similarly, the second decoupling unit 70 is used to generate a second decoupling signal according to the anti-noise signal output by the second active noise reduction filter unit 204.

(n)基本上等於第一訊號y ₁(n)。第二麥克風202接收到的第一誤差訊號e ₂(n)為[d ₂(n)+y ₁(n)+y ₂(n)]。接下來，第一解耦合訊號

(n)從第一誤差訊號e ₂(n)中扣除y ₁(n)成分，並將扣除y ₁(n)成分後的第一誤差訊號e ₂(n)(以下稱為訊號e ₂'(n))輸出至第二主動降噪濾波單元204。第二主動降噪濾波單元204所接收的訊號e ₂'(n)基本上等於d ₂(n)+y ₂(n)，換句話說，第二主動降噪濾波單元204不再受到第一訊號y ₁(n)的干擾。 First decoupling signal

( n ) is substantially equal to the first signal y1 ( n ). _The first error signal e2 ( n ) received by the second microphone 202 is _[ d2 ( n )+ y1 ( _n ) + y2 ( _n ) ]. Next, _the first decoupled signal

( n ) deducts _the y1 ( n) component from the first error signal e2(n ₎ , and outputs _the first error signal e2 ( n ) (hereinafter referred to as signal e2 _' ( n )) after deducting _{the y1} ( n ) component to the second active noise reduction filter unit 204. The signal e2 '( n ) received by the second active noise reduction filter unit 204 is substantially equal to d2 _{( n} ) + y2 ( n ) _. In other words, the second active noise reduction filter unit 204 is no longer interfered by the first signal y1 ( _n ).

(n)。第二解耦合訊號

(n)實質上等於訊號x ₂(n)。接下來，第二誤差訊號e ₁(n)中的訊號x ₂(n)成分會被移除，並將移除x ₂(n)成分後的第二誤差訊號e ₁(n)(以下稱為e ₁'(n))輸出至非主動降噪濾波單元1103，非主動降噪濾波單元1103所接收的訊號e ₁'(n)基本上等於d ₁(n)+x ₁(n)，因此非主動降噪濾波單元1103不受訊號x ₂(n)的干擾。 The second decoupling unit 70 includes a second channel analog filter 701 and a second adding circuit 702. The second channel analog filter 701 receives the second anti-noise signal y ₂ '( n ) output by the second active noise reduction filter unit 204 to generate a second decoupling signal

( n ). The second decoupling signal

( n ) is substantially equal to the signal x2 ( n ). Next, the signal x2 ( n ) component in the _second error signal _e1 ( n ) is removed, and the second error signal e1 ( n) after removing the x2(n ₎ component ₍ hereinafter referred to _as e1 _' ( n )) is output to the non-active noise reduction filter unit 1103. The signal _{e1 '} ( n ) received by the non-active noise reduction filter unit 1103 is substantially equal to d1 ( n )+ x1 ( n ₎ , so the non-active noise reduction filter unit 1103 is not interfered by _the signal x2 ( n ).

The present invention does not limit the implementation of the non-active noise reduction filter unit 1103. The non-active noise reduction filter unit 1103 can be set by any suitable non-active noise reduction filter required by the actual application. For example, the non-active noise reduction filter unit 1103 can be a HA filter with a weight marked as W _HA . For another example, the non-active noise reduction filter unit 1103 can be a PT filter with a weight marked as W _PT . For another example, the non-active noise reduction filter unit 1103 can be a PSAP filter with a weight marked as W _PSAP .

Except for the generation of the filter output y ' ₁ (n), the active noise reduction integrated circuit 110 shown in FIG. 14 has the same circuit architecture as the active noise reduction integrated circuit 20 shown in FIG. 7. Since those skilled in the art can easily understand the mathematical principles of the active noise reduction integrated circuit 110 shown in FIG. 14 after reading the above paragraphs on the active noise reduction integrated circuit 20 shown in FIG. 7, for the sake of brevity, further description is omitted here.

FIG15 is a schematic diagram of equivalent sampling time blocks of an active noise reduction headset with good isolation between the ear canal and the environment according to a preferred embodiment of the present invention. The active noise reduction headset in FIG15 is similar to the active noise reduction headset shown in FIG9 , but the difference between the two is that the active noise reduction integrated circuit 110 is used to stack at least one anti-noise signal and at least one non-anti-noise signal, and includes a non-active noise reduction filter unit 1103 replacing the first active noise reduction filter unit 203 shown in FIG9 . Therefore, in this embodiment, the first decoupling unit 40 receives the non-anti-noise signal y' ₁ ( n ) output from the non-active noise reduction filtering unit 1103, instead of the first anti-noise signal y' 1 ( n ) output from the first active noise reduction filtering unit 203, and the physical channel 205 transmits the non-anti-noise signal y ' ₁ ( n ) output _from the non-active noise reduction filtering unit 1103, instead of the first anti-noise signal y' ₁ ( n ) output from the first active noise reduction filtering unit 203.

For the non-active noise reduction filter unit 1103, the channel simulation filter 901 and the adding circuit 902 in the third decoupling unit 90 are used to eliminate the interference _{of the} signal y0 ( n ) (which is derived from the third anti-noise signal y'0 ( n ) transmitted via the physical channel 205), and the second decoupling unit 80 is used to eliminate the _interference of the signal y2 ( n ) (which is derived from _the second anti-noise signal y'2 ( n ) transmitted via the physical channel 205). For the second active noise reduction filter unit 204, the channel simulation filter 901 and the adding circuit 903 in the third decoupling unit 90 are used to eliminate the interference _of the signal y0 ( n ) (which is derived from _the third anti-noise signal y'0 ( n ) transmitted via the physical channel 205), and the first decoupling unit 40 is used to eliminate the interference _of the signal y1 ( n ) (which is derived from _the non-anti-noise signal y'1 ( n ) transmitted via the physical channel 205).

The present invention does not limit the implementation of the non-active noise reduction filter unit 1103. The non-active noise reduction filter unit 1103 can be set by any suitable non-active noise reduction filter required by the actual application. For example, the non-active noise reduction filter unit 1103 can be a HA filter with a weight marked as W _HA . For another example, the non-active noise reduction filter unit 1103 can be a PT filter with a weight marked as W _PT . For another example, the non-active noise reduction filter unit 1103 can be a PSAP filter with a weight marked as W _PSAP .

Except for the generation _of the filter output y'1 ( n ), the active noise reduction integrated circuit 110 shown in FIG. 15 has the same circuit architecture as the active noise reduction integrated circuit 20 shown in FIG. 9. Since those skilled in the art can easily understand the mathematical principles of the active noise reduction integrated circuit 110 shown in FIG. 15 after reading the above paragraphs on the active noise reduction integrated circuit 20 shown in FIG. 9, for the sake of brevity, further description is omitted here.

FIG. 16 is a flow chart of an active noise reduction method for stacking at least one anti-noise signal and at least one non-anti-noise signal according to a preferred embodiment of the present invention. Referring to FIG. 16 , the active noise reduction method for stacking at least one anti-noise signal and at least one non-anti-noise signal includes the following steps.

In step S1601, a first path is provided, and a first path non-anti-noise signal is output, wherein the first path non-anti-noise signal is converted into a first signal through a physical channel, and the first path includes: a non-active noise reduction filter unit for generating a non-anti-noise signal; a second path is provided, the second path receives an error signal containing a component of the first signal, and outputs a second path anti-noise signal to the physical channel, wherein the second path includes: an active noise reduction filter unit for generating an anti-noise signal, wherein the anti-noise signal derives the second path anti-noise signal.

In step S1602, the component of the first signal in the second path is removed based on the non-anti-noise signal. As shown in FIG. 11, based on the non-anti-noise signal and through the first channel analog filter 401, the component of the first signal y1 ( _n ) in the error signal e ( n ) to be received by the second active noise reduction filter unit 204 is removed at the input end of the second active noise reduction filter unit 204. As shown in FIG. 12, based on the non-anti-noise signal and through the first channel analog filter 501 and the third active noise reduction filter unit 502 (this unit has the same transfer function as the second active noise reduction filter unit), a decoupling signal is generated, and decoupling is performed at the output end of the second active noise reduction filter unit 204. As shown in FIG. 13 , a decoupling signal is generated based on the non-anti-noise signal through a channel simulation filter 602 and a third active noise reduction filter unit 601 (this unit has the same transfer function as the second active noise reduction filter unit), and decoupling is performed at the output end of the second active noise reduction filter unit 204. As shown in FIG. 14 , based on the non-anti-noise signal and through the first channel analog filter 401, at the input end of the second active noise reduction filter unit 204, the component of the first signal y ₁ ( n ) in the error signal e ₂ ( n ) to be received by the second active noise reduction filter unit 204 is removed; and based on the anti-noise signal and through the second channel analog filter 701, at the input end of the non-active noise reduction filter unit 1103, the component of the signal x ₂ ( n ) in the error signal e ₁ ( n ) to be received by the non-active noise reduction filter unit 1103 is removed.

In step S1603, the first path non-anti-noise signal and the second path anti-noise signal are played to eliminate noise.

Although the embodiments of Figures 1 to 9 and Figures 11 to 15 include the specific elements described above, it is not excluded that more additional elements may be used to achieve better technical effects without violating the spirit of the present invention. In addition, although the steps of Figures 10 and 16 are performed in a specified order, a person skilled in the art may modify the order of these steps without violating the spirit of the present invention, so the present invention is not limited to the order described above. In addition, a person skilled in the art may also integrate several steps into one step, or perform more steps sequentially or in parallel in addition to these steps, and the present invention is not limited thereto.

In the above embodiments, the active noise reduction integrated circuit can apply the decoupling technology proposed by the present invention to a combination of multiple active noise reduction filters, or can apply the decoupling technology proposed by the present invention to a combination of non-active noise reduction filters and active noise reduction filters. In fact, the same decoupling concept for interference reduction or performance enhancement can also be applied to any combination of filters used in the active noise reduction integrated circuit. Figure 17 shows an equivalent sampling time block diagram of an active noise reduction headset located between the ear canal and the environment in a preferred embodiment of the present invention. The active noise reduction earphone of FIG. 17 is similar to the active noise reduction earphone of FIG. 4, but the difference between the two is that the active noise reduction integrated circuit 170 includes a first filter unit 1703 and a second filter unit 1704, wherein the first filter unit 1703 replaces the first active noise reduction filter unit 203 shown in FIG. 4, and the second filter unit 1704 replaces the second active noise reduction filter unit 204 shown in FIG. 4. Each of the first filter unit 1703 and the second filter unit 1704 can be set by any suitable digital filter, depending on actual design considerations. Since after reading the above paragraphs on the active noise reduction integrated circuit 20 shown in FIG. 4 (or the active noise reduction integrated circuit 110 shown in FIG. 11), a person skilled in the art can easily understand the mathematical principle of the active noise reduction integrated circuit 170 shown in FIG. 17, for the sake of brevity, further description is omitted here.

Although the present invention is described using the above embodiments, it should be noted that these descriptions are not intended to limit the present invention. On the contrary, the present invention covers modifications and similar arrangements that are obvious to those skilled in the art. Therefore, the scope of the claims should be interpreted in the broadest way to include all obvious modifications and similar arrangements.

The above is only the preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

S1601, S1602, S1603: Steps

Claims (20)

An active noise reduction integrated circuit capable of stacking at least one anti-noise signal and at least one non-anti-noise signal comprises: a first path, outputting a first-path non-anti-noise signal, wherein the first-path non-anti-noise signal is converted into a first signal by a physical channel, the first path comprising: a non-active noise reduction filter unit, for generating a non-anti-noise signal; a second path, receiving an error signal containing a component of the first signal, and outputting a second-path anti-noise signal to the physical channel, the second path comprising: an active noise reduction filter unit, for generating an anti-noise signal, wherein the anti-noise signal derives the second-path anti-noise signal; and a first decoupling unit, for removing the component of the first signal in the second path based on the non-anti-noise signal. An active noise reduction integrated circuit that can stack at least one anti-noise signal and at least one non-anti-noise signal as described in claim 1, wherein the first decoupling unit includes: a first channel analog filter for simulating the physical channel and receiving the non-anti-noise signal to generate a first decoupled signal; and a first adding circuit, including a first input port, a second input port and an output port, wherein the first input port of the first adding circuit receives the first decoupling signal, the second input port of the first adding circuit receives the error signal, and the output port of the first adding circuit is coupled to the active noise reduction filter unit. An active noise reduction integrated circuit as described in claim 1 that can stack at least one anti-noise signal and at least one non-anti-noise signal, wherein the first decoupling unit includes: a first channel analog filter for simulating the physical channel and receiving the non-anti-noise signal to generate a first decoupling signal; and another active noise reduction filter unit, wherein the filtering operation of the other active noise reduction filter unit is the same as the filtering operation of the active noise reduction filter unit, wherein the other active noise reduction filter unit receives the first decoupling signal to generate another anti-noise signal; a first adding circuit, including a first input port, a second input port and a and an output port, wherein the first input port of the first adding circuit receives the other anti-noise signal, and the second input port of the first adding circuit receives the anti-noise signal; and a second adding circuit, comprising a first input port, a second input port and an output port, wherein the first input port of the second adding circuit is coupled to the output port of the first adding circuit, and the second input port of the second adding circuit receives the non-anti-noise signal, wherein, through the signal superposition of the first adding circuit and the second adding circuit, the non-anti-noise signal, the anti-noise signal and the first decoupling signal are synthesized into a noise reduction signal. An active noise reduction integrated circuit as described in claim 1 that can stack at least one anti-noise signal and at least one non-anti-noise signal, wherein the first decoupling unit includes: another active noise reduction filter unit, wherein the filtering operation of the other active noise reduction filter unit is the same as the filtering operation of the active noise reduction filter unit, wherein the other active noise reduction filter unit receives the non-anti-noise signal to generate another anti-noise signal; a first channel analog filter for simulating the physical channel and receiving the other anti-noise signal to generate a first decoupling signal; a first adding circuit including a first input port, a second input port and an input an output port, wherein the first input port of the first adding circuit receives the first decoupling signal, and the second input port of the first adding circuit receives the non-anti-noise signal; and a second adding circuit, comprising a first input port, a second input port and an output port, wherein the first input port of the second adding circuit is coupled to the output port of the first adding circuit, and the second input port of the second adding circuit receives the anti-noise signal, wherein, through the signal superposition of the first adding circuit and the second adding circuit, the non-anti-noise signal, the anti-noise signal and the first decoupling signal are synthesized into a noise reduction signal. An active noise reduction integrated circuit that can stack at least one anti-noise signal and at least one non-anti-noise signal as described in claim 1, wherein the physical channel is a first physical channel, wherein the second path anti-noise signal is converted into a second signal by a second physical channel, wherein the error signal is a first error signal, wherein the first path receives a second error signal containing a component of the second signal, wherein the active noise reduction integrated circuit further includes: a second decoupling unit for removing the component of the second signal in the first path based on the anti-noise signal. An active noise reduction integrated circuit as described in claim 1 that can stack at least one anti-noise signal and at least one non-anti-noise signal, wherein the second path anti-noise signal is converted into a second signal by the physical channel, the error signal includes a component of the second signal and a component of a third signal, the first path receives the error signal, and the active noise reduction integrated circuit further includes: a second decoupling unit for removing the second signal in the first path based on the anti-noise signal components; and a third path, outputting a third path anti-noise signal, wherein the third path anti-noise signal is converted from the physical channel into the third signal, the third path comprising: a third active noise reduction filter unit, for generating a third anti-noise signal; and a third decoupling unit, for removing the components of the third signal in the second path based on the third anti-noise signal, and removing the components of the third signal in the first path based on the third anti-noise signal. An active noise reduction integrated circuit as described in claim 1 that can stack at least one anti-noise signal and at least one non-anti-noise signal, wherein the non-active noise reduction filter unit is a hearing aid filter. An active noise reduction integrated circuit capable of stacking at least one anti-noise signal and at least one non-anti-noise signal as described in claim 1, wherein the non-active noise reduction filter unit is a transparent filter. An active noise reduction integrated circuit as described in claim 1 that can stack at least one anti-noise signal and at least one non-anti-noise signal, wherein the non-active noise reduction filter unit is a human voice amplification filter. An active noise reduction method capable of stacking at least one anti-noise signal and at least one non-anti-noise signal is applicable to an audio playback device having at least one active noise reduction filter unit and at least one non-active noise reduction filter unit. The active noise reduction method capable of stacking at least one anti-noise signal and at least one non-anti-noise signal comprises: providing a first path, outputting a first path non-anti-noise signal, wherein the first path non-anti-noise signal is converted into a first signal by a physical channel, and the first path comprises: a non-active noise reduction filter unit for producing A non-anti-noise signal is generated; a second path is provided to receive an error signal containing a component of the first signal, and a second path anti-noise signal is output to the physical channel, wherein the second path includes: an active noise reduction filter unit for generating an anti-noise signal, wherein the anti-noise signal derives the second path anti-noise signal; based on the non-anti-noise signal, the component of the first signal in the second path is removed; and based on the first path non-anti-noise signal and the second path anti-noise signal, the first path non-anti-noise signal and the second path anti-noise signal are played to eliminate noise. An active noise reduction method that can stack at least one anti-noise signal and at least one non-anti-noise signal as described in claim 10, wherein the step of removing the component of the first signal in the second path based on the non-anti-noise signal includes: converting the non-anti-noise signal into a decoupled signal according to the physical channel; and decoupling at the input end of the active noise reduction filter unit through the decoupling signal to remove the component of the first signal in the second path. An active noise reduction method that can stack at least one anti-noise signal and at least one non-anti-noise signal as described in claim 10, wherein the step of removing the component of the first signal in the second path based on the non-anti-noise signal includes: generating a decoupling signal according to the physical channel and the transfer function of the active noise reduction filter unit; and performing decoupling at the output end of the active noise reduction filter unit through the decoupling signal to remove the component of the first signal in the second path. An active noise reduction headset comprises: an active noise reduction integrated circuit capable of stacking at least one anti-noise signal and at least one non-anti-noise signal, comprising: a first path, outputting a first path non-anti-noise signal, wherein the first path non-anti-noise signal is converted into a first signal by a physical channel, the first path comprising: a non-active noise reduction filter unit, for generating a non-anti-noise signal; a second path, receiving an error signal containing a component of the first signal, and outputting a second path anti-noise signal to the physical channel, the second path comprising: an active A noise reduction filter unit is used to generate an anti-noise signal, wherein the anti-noise signal derives the second path anti-noise signal; and a first decoupling unit is used to remove the component of the first signal in the second path based on the non-anti-noise signal; and an audio conversion device, including: a speaker, used to play based on the first path non-anti-noise signal and the second path anti-noise signal to eliminate noise, wherein the speaker is part of the physical channel; and a microphone, used to receive the noise of the ear canal echo and convert it into the error signal. An active noise reduction headset as described in claim 13, wherein the first decoupling unit includes: a first channel analog filter for simulating the physical channel and receiving the non-noise-resistant signal to generate a first decoupling signal; and a first adding circuit including a first input port, a second input port and an output port, wherein the first input port of the first adding circuit receives the first decoupling signal, the second input port of the first adding circuit receives the error signal, and the output port of the first adding circuit is coupled to the active noise reduction filter unit. An active noise reduction headset as described in claim 13, wherein the first decoupling unit comprises: a first channel analog filter for simulating the physical channel and receiving the non-anti-noise signal to generate a first decoupling signal; and another active noise reduction filter unit, wherein the filtering operation of the other active noise reduction filter unit is the same as the filtering operation of the active noise reduction filter unit, wherein the other active noise reduction filter unit receives the first decoupling signal to generate another anti-noise signal; a first adding circuit comprising a first input port, a second input port and an output port, wherein the The first input port of the first adding circuit receives the other anti-noise signal, and the second input port of the first adding circuit receives the anti-noise signal; and a second adding circuit includes a first input port, a second input port and an output port, wherein the first input port of the second adding circuit is coupled to the output port of the first adding circuit, and the second input port of the second adding circuit receives the non-anti-noise signal, wherein, through the signal superposition of the first adding circuit and the second adding circuit, the non-anti-noise signal, the anti-noise signal and the first decoupling signal are synthesized into a noise reduction signal. An active noise reduction headset as described in claim 13, wherein the first decoupling unit includes: another active noise reduction filter unit, wherein the filtering operation of the other active noise reduction filter unit is the same as the filtering operation of the active noise reduction filter unit, wherein the other active noise reduction filter unit receives the non-anti-noise signal to generate another anti-noise signal; a first channel analog filter for simulating the physical channel and receiving the other anti-noise signal to generate a first decoupling signal; a first adding circuit including a first input port, a second input port and an output port, wherein the first adding circuit The first input port of the adding circuit receives the first decoupling signal, and the second input port of the first adding circuit receives the non-anti-noise signal; and a second adding circuit includes a first input port, a second input port and an output port, wherein the first input port of the second adding circuit is coupled to the output port of the first adding circuit, and the second input port of the second adding circuit receives the anti-noise signal, wherein the non-anti-noise signal, the anti-noise signal and the first decoupling signal are synthesized into a noise reduction signal by superimposing the signals of the first adding circuit and the second adding circuit. An active noise reduction headset as described in claim 13, wherein the physical channel is a first physical channel, wherein the second path anti-noise signal is converted into a second signal by a second physical channel, wherein the error signal is a first error signal, wherein the first path receives a second error signal containing a component of the second signal, and wherein the active noise reduction integrated circuit further includes: a second decoupling unit for removing the component of the second signal in the first path based on the anti-noise signal. An active noise-cancelling headset as described in claim 13, wherein the non-active noise-cancelling filter unit is a hearing aid filter. An active noise-cancelling headset as described in claim 13, wherein the non-active noise-cancelling filter unit is a transparent filter. An active noise-canceling headset as described in claim 13, wherein the non-active noise-canceling filter unit is a human voice amplifying filter.