KR102869994B1 - Method and apparatus for removing noise using phase shift - Google Patents

Abstract

A noise removal method using phase shift according to one embodiment of the present invention may include a step of calculating a delay time based on at least one of an audio hardware buffer size, a software buffer size, and a buffer size for a sound transmission speed generated by a medium thickness, a step of generating a reference frequency based on an input signal and the delay time, a step of generating a multiple frequency composed of n in-phase frequencies based on the reference frequency, a step of calculating a phase shift value based on the reference frequency, and a step of generating an inverse signal for the input signal based on the phase shift value.

Description

Method and apparatus for removing noise using phase shift

The present invention relates to a noise removal method and device for removing noise generated in the surrounding environment.

In general, it's no exaggeration to say that people living in modern society live amidst environmental pollution and hazards brought on by industrial development. Furthermore, they must live amidst a deluge of noise, and noise, as a form of environmental pollution, inflicts enormous psychological damage on modern people.

Acoustic signals, including noise, fundamentally have characteristics such as frequency, amplitude, and phase, and in general, these acoustic signals create their own unique sound by summing up countless frequency components (including unique amplitude and phase characteristics).

Conventional noise removal techniques generate a signal identical to the input signal, invert the generated signal to create an inverse signal, and then combine the inverse signal with the input signal to remove noise. This noise removal technique can achieve perfect noise removal if there is no delay time difference between the input signal and the inverse signal.

However, in systems that use digital processing, the speed of digital conversion and processing causes a delay in signal processing, which causes a delay time difference between the input signal and the inverse signal.

The phase difference between the input signal and the reverse signal occurs due to the delay time difference generated as described above, making noise removal difficult.

The purpose of the present invention is to provide a method and device for removing noise by calculating a phase difference caused by a delay time, generating a reverse signal reflecting a phase shift regardless of the delay time, and using the generated reverse signal.

A noise removal method using phase shift according to an embodiment for achieving the above object may include a step of calculating a delay time based on at least one of an audio hardware buffer size, a software buffer size, and a buffer size for a sound transmission speed caused by a medium thickness, a step of generating a reference frequency based on an input signal and the delay time, a step of generating a multiple frequency composed of n in-phase frequencies based on the reference frequency, a step of calculating a phase shift value based on the reference frequency, and a step of generating an inverse signal for the input signal based on the phase shift value.

The above audio hardware buffer size may include at least one of a buffer size generated during an ADC conversion process, a process of transmitting an AD-converted digital signal to a CPU, a process of transmitting a signal processed by the CPU to a DAC, and a DAC conversion process.

The above software buffer size may include the size of the buffer currently used during the software design process or operation process.

The above reference frequency can be calculated as a value obtained by dividing the sample rate sampled for the input signal by the delay time.

The above reference frequency may be a frequency at which the sum of the phase value of the input signal and the phase value of the reverse signal first becomes 0.

The above multiple frequency can be calculated by adding the interval of the multiple frequency to the above reference frequency.

The interval of the above multiple frequencies can be calculated by multiplying the reference frequency by the value obtained by dividing the frequency removal reference range (Process Range) by 360.

The above phase change value can be calculated by obtaining a reference frequency corresponding to the buffer size, dividing the process range by the reference frequency to obtain the size of the phase change value that changes in units of 1 Hz, and multiplying the unit phase change value by the frequency of the input signal.

The above-mentioned reverse signal can be generated by inverting the phase value of the input signal frequency.

A noise removal device using a phase shift according to an embodiment for achieving the above object may include a delay time calculation unit for calculating a delay time based on at least one of an audio hardware buffer size, a software buffer size, and a buffer size for a sound transmission speed generated by a medium thickness, a reference frequency generation unit for generating a reference frequency based on an input signal and the delay time, a multiple frequency generation unit for generating a multiple frequency composed of n in-phase frequencies based on the reference frequency, a phase change value calculation unit for calculating a phase change value based on the reference frequency, and an antiphase signal generation unit for generating an antiphase signal for the input signal based on the phase change value.

The above audio hardware buffer size may include at least one of a buffer size generated during an ADC conversion process, a process of transmitting an AD-converted digital signal to a CPU, a process of transmitting a signal processed by the CPU to a DAC, and a DAC conversion process.

The above software buffer size may include the size of the buffer currently used during the software design process or operation process.

The above reference frequency can be calculated as a value obtained by dividing the sample rate sampled for the input signal by the delay time.

The above reference frequency may be a frequency at which the sum of the phase value of the input signal and the phase value of the reverse signal first becomes 0.

The above multiple frequency can be calculated by adding the interval of the multiple frequency to the above reference frequency.

The interval of the above multiple frequencies can be calculated by multiplying the reference frequency by the value obtained by dividing the frequency removal reference range (Process Range) by 360.

The above phase change value can be calculated by obtaining a reference frequency corresponding to the buffer size, dividing the process range by the reference frequency to obtain the size of the phase change value that changes in units of 1 Hz, and multiplying the unit phase change value by the frequency of the input signal.

The above-mentioned reverse signal can be generated by inverting the phase value of the input signal frequency.

The embodiment can effectively remove noise by generating an inverse signal that takes delay time into account in a digital environment where delay time inevitably occurs for data processing.

In addition, the embodiment can effectively generate an inverse signal by making the sum of all phase values of the input signal and all phase values of the inverse signal that cancels the input signal equal.

Fig. 1 is a block diagram showing a noise reduction device according to an embodiment.
Fig. 2 is a graph showing an input signal input to a noise reduction device according to an embodiment.
Fig. 3 is a graph showing a reverse signal generated by a noise cancellation device according to an embodiment.
Fig. 4 is a graph showing a sum signal obtained by adding an input signal and a reverse signal according to an embodiment.
Fig. 5 is a block diagram showing a detailed configuration of a noise reduction device according to an embodiment.
Fig. 6 is a diagram showing a buffer structure of audio hardware and software according to an embodiment.
Fig. 7 is a graph for explaining the reference frequency according to the embodiment.
Fig. 8 is a graph for explaining the multiplication frequency according to an embodiment.
Fig. 9 is a graph showing an explanation of detailed points to explain the process of calculating a phase change value according to an embodiment.
Fig. 10 is a flowchart illustrating a noise removal method using phase shift according to an embodiment.

The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals designate like elements throughout the specification.

Although "first" or "second" are used to describe various components, these components are not limited by such terms. Such terms may only be used to distinguish one component from another. Accordingly, a first component referred to below may also be a second component within the technical scope of the present invention.

The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise. As used herein, the terms "comprises" or "comprising" imply that a stated component or step does not exclude the presence or addition of one or more other components or steps.

Unless otherwise defined, all terms used herein are to be interpreted as having a meaning commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

In this document, each of the phrases “A or B,” “at least one of A and B,” “at least one of A or B,” “at least one of A, B, or C,” and “at least one of A, B, or C” may include any one of the items listed with that phrase, or all possible combinations thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. When describing with reference to the drawings, identical or corresponding components are given the same drawing reference numerals, and redundant descriptions thereof will be omitted.

FIG. 1 is a block diagram showing a noise removal device according to an embodiment, FIG. 2 is a graph showing an input signal input to a noise removal device according to an embodiment, FIG. 3 is a graph showing a reverse signal generated in a noise removal device according to an embodiment, and FIG. 4 is a graph showing a sum signal obtained by adding an input signal and a reverse signal according to an embodiment.

Referring to FIG. 1, a noise removal device (200) according to an embodiment can generate an inverse signal for an input signal (100) and generate a sum signal (300) by adding the inverse signal to the input signal. The sum signal can be a signal from which noise has been removed from the input signal.

Unlike conventional technology, the noise removal device (200) can generate an inverse signal by utilizing phase shift according to delay time.

Input signals (100) may include, but are not limited to, noise between floors, vehicles and other means of transportation, industrial noise-generating equipment such as compressors and electric motors, noise-generating elements in household appliances such as hair dryers and washing machines, and military equipment sensitive to noise generation.

As illustrated in Fig. 2, the input signal may include white noise. The input signal may be a composite file composed of multiple sine waves.

As illustrated in FIG. 3, the noise removal device (200) can generate an inverse signal corresponding to an input signal. The inverse signal may be a signal capable of canceling out the input signal (100).

The noise removal device (200) can decompose the composite wave, which is the input signal (100), through Fourier transform and obtain the wavelength value for each decomposed frequency. The noise removal device (200) can remove noise of all frequencies constituting the composite wave by obtaining the inverse value corresponding to each frequency constituting the composite wave.

The noise removal device (200) cannot generate the same reverse signal based on the input signal (100) due to the delay time when generating the reverse signal for the input signal.

Accordingly, the noise removal device (200) according to the embodiment can generate a reverse signal by taking the delay time into consideration. For example, the noise removal device (200) can generate a reverse signal by calculating the phase when the phase of the input signal (100) reaches the delay time position.

A sum signal can be generated by adding an inverse signal generated by a noise removal device (200) to an input signal, as shown in FIG. 4.

A noise removal device according to an embodiment can generate an inverse signal and use it for noise removal without having to analyze the type and characteristics of the waveform, regardless of the input complex wave.

Fig. 5 is a block diagram showing a detailed configuration of a noise reduction device according to an embodiment.

Referring to FIG. 5, a noise removal device (200) according to an embodiment may include a delay time calculation unit (210), a reference frequency generation unit (230), a multiple frequency generation unit (250), a phase change value calculation unit (270), and a reverse signal generation unit (290).

The delay time calculation unit (210) can calculate the delay time using at least one of the audio hardware buffer size and the software buffer size.

Fig. 6 is a diagram showing a buffer structure of audio hardware and software according to an embodiment.

The audio hardware buffer size (L1) may include at least one of a unique buffer size during the ADC conversion process, a system buffer size for transmitting a digital signal to a central processing unit (CPU) during AD conversion, and a system buffer size for transmitting a signal processed in the CPU to the DAC.

The software buffer size (L2) may include the size of the buffer currently used in the operation process, for example, the buffer size according to the time value to be processed or the target frequency during the processor processing process.

Since the audio hardware buffer size (L1) and software buffer size (L2) are determined during the design and setup phase, the audio hardware buffer size (L1) and software buffer size (L2) can be confirmed in advance.

In addition, the delay time calculation unit (210) can calculate the delay time by considering the sound transmission speed caused by the thickness of the medium.

The sound transmission velocity due to medium thickness can be determined based on the type of medium through which sound is transmitted. Since there is no frequency variation, knowing the sound transmission velocity of a medium allows for the calculation of the delay time due to medium thickness.

Since the propagation speed of sound in a medium can be known and converted into a delay time, the delay time can be calculated by taking into account the propagation speed of sound caused by the thickness of the medium.

Conversely, since the purely mechanical delay time values caused by the operations of AD, DA, and DSP can be known, the thickness value of the medium can be calculated by subtracting the sum of the mechanical delay times from the total delay time.

Returning to Figure 5, the reference frequency generator (230) can be generated based on the input signal and delay time.

Fig. 7 is a graph for explaining the reference frequency according to the embodiment.

As illustrated in Fig. 7, the reference frequency (f(0)) may be the frequency at which the phase becomes initially "0" Deg when the input signal and the inverse signal are added.

The reference frequency f(0) can be calculated by mathematical expression 1.

[Mathematical Formula 1]

Here, the sample rate can be a sampled value for the input signal.

For example, if the sample rate is 96000 Hz and the total delay time (Buffer Size) is 256, the reference frequency can be 375 Hz.

Mathematical expression 1 can be used in digital conversion, and since the speed of sound can be substituted instead of the sample rate, it becomes possible to obtain a reference frequency value without considering the speed in the medium.

Returning to FIG. 5, the multiple frequency generation unit (250) can generate a multiple frequency based on a reference frequency.

Fig. 8 is a graph for explaining the multiplication frequency according to an embodiment.

As illustrated in Fig. 8, the multiple frequency can be composed of n in-phase frequencies depending on the reference frequency. When the phase angle of the reference frequency is -360 Deg, the phase value of the multiple frequency can be -360 Deg.

Since the multiple frequency means the frequency at which the period of the phase repeats the process range set, the interval f(i) of the multiple frequency can be defined as in mathematical expression 2.

[Equation 2]

Here, the process range may mean the frequency removal reference range in the entire removal process.

For example, if f(0)=375Hz and the process range is 720 Deg, the interval of the multiple frequencies can be 375x(720/360)= 750Hz.

The multiple frequency f(mn) can be determined by mathematical expression 3. The multiple frequency can be obtained by adding the interval of multiple frequencies starting from the reference frequency.

[Equation 3]

Here, f(in) can mean the interval of the nth frequency.

For example, if f(0)=375Hz and the process range is 720 Deg, the interval of the multiple frequencies is 375x(720/360)=750Hz, the 0th multiple frequency can be 375+(750x0)=375Hz, the 1st multiple frequency can be 375+(750x1)=1125Hz, and the 2nd multiple frequency can be 375+(750x2)=1175Hz. The Nth multiple frequency can be calculated in the same way.

Returning to Figure 5, the phase change value calculation unit (270) can calculate the phase change value based on the reference frequency.

Fig. 9 is a graph showing an explanation of detailed points to explain the process of calculating a phase change value according to an embodiment.

As illustrated in Fig. 9, when n repetition frequencies are generated starting from a reference frequency, the total phase angle of the reference frequency has a range of 360 Deg, and it can be seen that the frequency repeated every 720 Deg angle (phase) is a multiple frequency. Consequently, the phase angle can be calculated in units of 1 Hz as in mathematical equation 4.

[Equation 4]

For example, if the reference frequency f(0) = 375 Hz, the phase angle can be 360/375 = 0.96 Deg. In other words, it can be seen that an angle change (phase change) of 0.96 Deg occurs per 1 Hz.

Wavelength can be defined as the value of wave propagation per unit length. The unit length of the wavelength is set as the buffer size, and it can mean the number of cycles repeated within the buffer size. Here, the wavelength can be equal to a multiple of the reference frequency or a multiple of the repetition frequency, depending on the selected process range. The wavelength can have a phase range from 0° to +360° or from 0° to -360°.

Assuming that the starting point of the phase of the frequency of the input signal is 0 Deg, the change in phase after a certain period of time corresponding to the buffer size can be obtained.

First, the reference frequency corresponding to the buffer size is obtained, and the size of the phase angle (phase change value) that changes in units of 1 Hz from the reference frequency is obtained, and the phase change value can be calculated by multiplying the frequency of the input signal by the unit phase angle (phase change value).

For example, if the sample rate is 96000, the buffer size is 256, and the input frequency (f(in)) is 500 Hz, the reference frequency can be f(0)=96000/256=375 Hz. The phase angle can be 360/375 Hz=0.96 Deg. If you multiply the frequency of the input frequency by the unit phase angle, it can be 500x0.96=480 Deg.

That is, when a 500Hz signal is input, it can mean that after a time corresponding to the buffer size has passed, the phase angle will have a value of 480 Deg.

The total phase change angle existing between the input point and the buffer size time, without considering the period of the repeating phase, can be defined as the input cumulative angle.

Input cumulative angle can be defined as the phase angle of the input frequency x 1Hz, as shown in mathematical expression 5.

[Equation 5]

From Equation 5, we can see that when the input signal is 500 Hz, the cumulative angle is 480 Deg. However, since the cycle repeats every 360 Deg, the phase angle can be 480-360=120 Deg.

That is, since the value of 1 wave can be converted to 360 Deg, the input cumulative angle can be defined by mathematical expression 6.

[Equation 6]

Here, the frequency can mean an integer value with the decimal point discarded.

Therefore, the input cumulative angle can be defined as in mathematical expression 7.

[Equation 7]

The angle at which the sum of the input phase angle and the sum of the angles of the reverse signal become 0 Deg can be expressed as the removed phase angle for generating a reverse signal of the input phase angle.

For example, since the input phase angle for 500 Hz is calculated as 480 Deg, the reverse phase angle can be -480 Deg.

As described above, the reverse signal generation unit (290) can generate a reverse signal for the input signal based on the phase change value.

Since the phase value of the input frequency and the phase value of the reverse signal must be 0, this can mean that the sum of the accumulated phase values of the input frequency and the accumulated phase value of the reverse signal is 0. Accordingly, the sum of the phase values of the reverse frequency is equal to the sum of the phase angles, and only the phase value can have a (-) value.

If we introduce the wavenumber here, the wavenumber can be defined as in mathematical expression 8.

[Equation 8]

Therefore, the sum of all phases of removal can be the sum of phase values of the first wave number + ?? + the sum of phase values of the nth wave number.

Meanwhile, frequencies can be divided using octaves. Increasing the octave number decreases resolution, while decreasing the octave number increases resolution.

Therefore, the low-frequency range that requires detailed control in frequency resolution settings can be subdivided, and the high-frequency range that does not require detailed control can be set simply, maximizing the efficiency of the DSP.

Additionally, resolution settings can be applied concisely and a precise number of points can be specified. Furthermore, different octaves can be applied to each band to focus on specific frequency bands, thereby increasing precision.

Additionally, different octave constants can be applied to each octave. The greatest advantage of octave division is that it has the same frequency across all octaves. This can be utilized to increase or decrease the number of generated frequencies by assigning different octave constants to each octave.

For example, frequencies one octave above the reference frequency can be divided into 1/12 octaves, and frequencies two octaves above the reference frequency can be divided into 1/6 octaves.

Using the above method, the frequency division of the target specific frequency band can be further refined, enabling more precise removal angle adjustment.

Fig. 10 is a flowchart illustrating a noise removal method using phase shift according to an embodiment.

Referring to FIG. 10, a noise removal method using a phase shift according to an embodiment may include a step of calculating a delay time (S100), a step of generating a reference frequency (S200), a step of generating a multiple frequency (S300), a step of calculating a phase shift value (S400), and a step of generating a reverse signal (S500). Here, the noise removal method using a phase shift according to an embodiment may be performed in a noise removal device using a phase shift according to an embodiment.

The noise cancellation device can calculate a delay time based on at least one of an audio hardware buffer size and a software buffer size (S100).

The audio hardware buffer size may include at least one of a unique buffer size during the ADC conversion process, a system buffer size for transmitting a digital signal to a central processing unit (CPU) during AD conversion, and a system buffer size for transmitting a signal processed in the CPU to the DAC.

The software buffer size may include the size of the buffer currently used during the operation process, for example, the buffer size according to the time value to be processed during the processor processing process or the target frequency.

Since the audio hardware buffer size and software buffer size are determined during the design and setup phase, you can check the audio hardware buffer size and software buffer size in advance.

In addition, the delay time can be calculated by taking into account the sound transmission speed caused by the thickness of the medium.

The noise cancelling device can generate a reference frequency (S200).

The noise canceling device can generate a reference frequency based on an input signal and a delay time. Here, the reference frequency can be a frequency at which the phase initially becomes "0" degrees when the input signal and an inverse signal are added.

The noise canceling device can calculate the reference frequency by dividing the sample rate sampled for the input signal by the total delay time.

The noise canceling device can generate a multiple frequency based on a reference frequency (S300).

A multiple frequency can be composed of n in-phase frequencies depending on the reference frequency. If the phase angle of the reference frequency is -360 Deg, the phase value of the multiple frequency can be -360 Deg.

The multiple frequency can be obtained by adding the interval of the multiple frequency starting from the reference frequency.

The noise cancellation device can calculate a phase change value based on a reference frequency (S400).

The noise cancellation device can obtain the phase change value after a certain period of time corresponding to the buffer size, assuming that the phase starting point of the frequency of the input signal is 0 Deg.

First, the reference frequency corresponding to the buffer size is obtained, and the size of the phase angle is obtained by changing the reference frequency by 1 Hz, and the phase change value can be calculated by multiplying the unit phase angle by the frequency of the input signal.

The noise canceling device can generate an inverse signal based on the phase shift value (S500).

The noise canceling device can generate a reverse signal such that the sum of the phase values of the input frequency and the phase values of the reverse signal becomes 0, and from this, the reverse signal can be generated such that the sum of the accumulated phase values of the input frequency and the accumulated phase values of the reverse signal becomes 0. Accordingly, the sum of the phase values of the reverse frequencies is equal to the sum of the phase angles, and only the phase value can have a (-) value.

Finally, the noise removal device can remove noise by adding an inverse signal to the input signal to generate a sum signal.

Various embodiments of the present document may be implemented as software (e.g., a program) including instructions stored in a machine-readable storage medium (e.g., memory (internal memory or external memory)) that can be read by a machine (e.g., a computer). The device may include an electronic device according to the disclosed embodiments, which is a device that can call instructions stored in the storage medium and operate according to the called instructions. When the instructions are executed by a control unit, the control unit may directly or under the control of the control unit use other components to perform a function corresponding to the instructions. The instructions may include code generated or executed by a compiler or an interpreter. The machine-readable storage medium may be provided in the form of a non-transitory storage medium. Here, non-transitory means that the storage medium does not contain signals and is tangible, but does not distinguish between data being stored semi-permanently or temporarily in the storage medium.

According to an embodiment, the method according to various embodiments disclosed in the present document may be provided as included in a computer program product.

According to one embodiment, a computer-readable recording medium storing a computer program may include instructions for causing a processor to perform a method, the method including calculating a delay time based on at least one of an audio hardware buffer size, a software buffer size, and a buffer size for a sound propagation speed caused by a medium thickness, generating a reference frequency based on an input signal and the delay time, generating a multiple frequency composed of n in-phase frequencies based on the reference frequency, calculating a phase shift value based on the reference frequency, and generating an inverse signal for the input signal based on the phase shift value.

According to one embodiment, a computer program stored in a computer-readable recording medium may include instructions for causing a processor to perform a method, the method including calculating a delay time based on at least one of an audio hardware buffer size, a software buffer size, and a buffer size for a sound propagation speed caused by a medium thickness, generating a reference frequency based on an input signal and the delay time, generating a multiple frequency composed of n in-phase frequencies based on the reference frequency, calculating a phase shift value based on the reference frequency, and generating an inverse signal for the input signal based on the phase shift value.

The specific implementations described in the present invention are exemplary and do not limit the scope of the present invention in any way. For the sake of brevity, descriptions of conventional electronic components, control systems, software, and other functional aspects of the systems may be omitted. In addition, the lines connecting or connecting members between components depicted in the drawings are merely representative of functional connections and/or physical or circuit connections, and may be replaced or represented as various additional functional connections, physical connections, or circuit connections in an actual device. Furthermore, unless specifically mentioned as "essential," "important," etc., a component may not be absolutely necessary for the application of the present invention.

Therefore, the idea of the present invention should not be limited to the embodiments described above, and not only the scope of the patent claims described below but also all scopes equivalent to or equivalently modified from the scope of the patent claims are considered to fall within the scope of the idea of the present invention.

100: Input signal
200: Noise Cancelling Device
210: Delay time calculation unit
230: Reference frequency generator
250: Multiple frequency generator
270: Phase change value calculation unit
290: Reverse signal generation unit

Claims (18)

A step of calculating a delay time based on at least one of an audio hardware buffer size, a software buffer size, and a buffer size for a sound transmission speed caused by a medium thickness;
A step of generating a reference frequency based on an input signal and the delay time;
A step of generating a multiple frequency composed of n in-phase frequencies based on the above reference frequency;
A step of calculating a phase change value based on the above reference frequency; and
A step of generating an inverse signal for the input signal based on the phase change value;
Including,
A noise removal method using a phase shift in which the above reference frequency is calculated as a value obtained by dividing the sample rate sampled for the above input signal by the delay time. In the first paragraph,
The above audio hardware buffer size is a noise removal method using phase shift including at least one of a buffer size generated during an ADC conversion process, a process of transmitting an AD-converted digital signal to a CPU, a process of transmitting a signal processed by the CPU to a DAC, and a DAC conversion process. In the first paragraph,
The above software buffer size is a noise removal method using phase shift including the size of the buffer currently used in the software design process or operation process. delete In the first paragraph,
The above reference frequency is a noise removal method using phase shift, which is a frequency at which the sum of the phase value of the input signal and the phase value of the reverse signal first becomes 0. In the first paragraph,
A noise removal method using a phase shift in which the above multiple frequency is calculated by adding the interval of the above multiple frequency to the above reference frequency. In paragraph 6,
A noise removal method using a phase shift in which the interval of the above multiple frequencies is calculated by multiplying the value obtained by dividing the frequency removal reference range (Process Range) by 360 by the above reference frequency. In the first paragraph,
The above phase change value is a noise removal method using phase shift, which is calculated by obtaining a reference frequency corresponding to the buffer size, dividing the process range by the reference frequency to obtain the phase change value size that changes in units of 1 Hz, and multiplying the unit phase change value by the frequency of the input signal. In the first paragraph,
The above-mentioned reverse signal is a noise removal method using a phase shift generated by inverting the phase value of the input signal frequency. A delay time calculation unit for calculating a delay time based on at least one of an audio hardware buffer size, a software buffer size, and a buffer size for a sound transmission speed caused by a medium thickness;
A reference frequency generation unit that generates a reference frequency based on an input signal and the delay time;
A multiple frequency generation unit that generates a multiple frequency composed of n in-phase frequencies based on the above reference frequency;
A phase change value calculation unit that calculates a phase change value based on the above reference frequency; and
A reverse signal generation unit that generates a reverse signal for the input signal based on the phase change value;
Including,
A noise removal device using a phase shift in which the above reference frequency is calculated as a value obtained by dividing the sample rate sampled for the above input signal by the delay time. In Article 10,
The above audio hardware buffer size is a noise removal device using phase shift including at least one of a buffer size generated during an ADC conversion process, a process of transmitting an AD-converted digital signal to a CPU, a process of transmitting a signal processed by the CPU to a DAC, and a DAC conversion process. In Article 10,
The above software buffer size is a noise removal device using phase shift including the size of the buffer currently used in the software design process or operation process. delete In Article 10,
A noise removal device using a phase shift, wherein the above reference frequency is a frequency at which the sum of the phase value of the input signal and the phase value of the reverse signal first becomes 0. In Article 10,
A noise removal device using a phase shift in which the above multiple frequency is calculated by adding the interval of the above multiple frequency to the above reference frequency. In Article 15,
A noise removal device using a phase shift in which the interval of the above multiple frequencies is calculated by multiplying the value obtained by dividing the frequency removal reference range (Process Range) by 360 by the above reference frequency. In Article 10,
The above phase change value is a noise removal device using a phase shift that is calculated by obtaining a reference frequency corresponding to the buffer size, dividing the process range by the reference frequency to obtain the phase change value size that changes in units of 1 Hz, and multiplying the unit phase change value by the frequency of the input signal. In Article 10,
The above-mentioned reverse signal is a noise removal device that utilizes a phase shift generated by inverting the phase value of the input signal frequency.