JP2018163304A - Signal processing apparatus and active noise cancellation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate a noise canceling signal capable of more effectively canceling noise by detecting abnormal noise such as wind noise from environmental noise. SOLUTION: Two or more input units, which are arranged in a first output unit and a second output unit of different channels for outputting sound and detect environmental noise, and environmental noise detected by two or more input units, respectively. The cancel noise signal generation unit that generates a cancel noise signal, the abnormal noise detection unit that detects abnormal noise from the environmental noise detected by two or more input units, and the cancellation noise signal according to the detection result of the abnormal noise detection unit. Provided is a signal processing device including an adjusting unit for adjusting the level of a cancel noise signal output from a generation unit and a first mixer for mixing the cancel noise signal and the reproduced signal. [Selection diagram] Fig. 1

Description

  The present invention relates to a signal processing device and an active noise cancellation system.

  ANC (active noise cancellation) is a technique that has been conventionally realized with earphones and headphones. For example, ambient sound is captured as environmental sound (environmental noise) with a microphone incorporated in an earphone, and the phase of the captured sound is inverted and added to a reproduction signal from a speaker. Noise entering the inside of the earphone from the outside is canceled by the signal whose phase is inverted, and the user can hear only the reproduction signal from the speaker.

In the conventional ANC, when a strong wind hits the microphone and a wind noise is generated, it is output from the speaker as a large noise together with the reproduction signal, which may cause discomfort to the user. Since the wind noise is not noise that enters the earphone from the outside, the cancel noise signal is not appropriate, and extra components related to the wind noise are output (see Patent Documents 1 and 2).
Patent Document 1 Japanese Patent Application Laid-Open No. 2008-60759 Patent Document 2 US Pat.

  In the noise canceling process, it is desired to detect an abnormal sound such as a wind noise from the environmental noise and generate a noise canceling signal so as not to make the user uncomfortable.

  In the first aspect of the present invention, two or more input units for detecting environmental noise, and two or more input units, which are arranged in the first output unit and the second output unit of different channels that output sound, respectively. From the detected environmental noise, a cancellation noise signal generation unit that generates a cancellation noise signal, an abnormal sound detection unit that detects abnormal noise from environmental noise detected by two or more input units, and a detection result of the abnormal noise detection unit Accordingly, a signal processing device is provided that includes an adjustment unit that adjusts the level of the cancellation noise signal output from the cancellation noise signal generation unit, and a first mixer that mixes the cancellation noise signal and the reproduction signal.

  According to a second aspect of the present invention, there is provided an active noise cancellation system comprising the signal processing device of the first aspect and a signal source for outputting a reproduction signal.

  The above summary of the present invention does not enumerate all of the features of the present invention. A sub-combination of these feature groups can also be an invention.

The structure of the active noise cancellation system which concerns on this embodiment is shown. The block diagram of the 1st structural example of the active noise cancellation system which concerns on this embodiment is shown. The block diagram of an abnormal sound detection part is shown. The flowchart of the noise cancellation operation | movement of the active noise cancellation system which concerns on this embodiment is shown. The block diagram of the 2nd structural example of the active noise cancellation system which concerns on this embodiment is shown.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 shows a configuration of an active noise cancellation system 100 according to the present embodiment. The active noise cancellation system 100 performs noise cancellation processing on the reproduction signal supplied from the signal source 110 using the environmental noise detected by the input units 210 and 215 in the signal processing device 120, and the noise cancellation processing is performed. The signal is output from the first output unit 200 and the second output unit 205.

  FIG. 2 is a block diagram of a first configuration example of the active noise cancellation system 100 according to the present embodiment. The active noise cancellation system 100 includes a signal source 110 and a signal processing device 120.

  The signal source 110 supplies a reproduction signal such as a music signal. The signal source 110 may generate and supply a reproduction signal from digital data stored in a storage device such as a CD, a DVD, a hard disk drive, or a flash memory. In addition, the signal source 110 may receive data wirelessly from a specific website or cloud service and generate a reproduction signal.

  The signal processing device 120 mixes and outputs a noise cancellation signal to the reproduction signal supplied from the signal source 110. For example, the signal processing device 120 may be a DSP (digital signal processor). The signal processing device 120 includes a first output unit 200, a second output unit 205, two or more input units 210 and 215, an abnormal sound detection unit 220, an adjustment unit 230, a cancellation noise signal generation unit 240, A first mixer 250.

  The first output unit 200 and the second output unit 205 receive the signal processed reproduction signal, convert it into an acoustic signal, and output a sound such as music. When the received signal is a digital signal, the first output unit 200 and the second output unit 205 may perform analog-to-analog conversion on the signal to generate an analog signal, amplify the analog signal, and output the sound as sound. . The first output unit 200 and the second output unit 205 have different channels. For example, the first output unit 200 is a right channel and the second output unit 205 is a left channel, and may be provided in separate housings. . As an example, the first output unit 200 and the second output unit 205 may include earphones or headphones.

  Two or more input units 210 and 215 are arranged in the first output unit 200 and the second output unit 205, respectively, and detect ambient environmental noise. The two or more input units 210 and 215 may convert the input environmental noise into an electric signal, convert the electric signal into a digital signal, and output the digital signal. The two input units 210 and 215 are each incorporated into a case provided with the first output unit 200 and a case provided with the second output unit 205, respectively, so that the signal processing device 120 can be used. The input units 210 and 215 are arranged apart from each other at a predetermined interval. A plurality of two or more input units 210 and 215 may be provided in at least one of the first output unit 200 and the second output unit 205. The two inputs 210 and 215 may be channels different from each other, and may be a right channel microphone and a left channel microphone as an example.

  The abnormal noise detection unit 220 is connected to the outputs of the two or more input units 210 and 215, detects abnormal noise from the environmental noise detected by the two or more input units 210 and 215, and outputs a detection result. The abnormal sound detection unit 220 may output, for example, a gain setting value used in the adjustment unit 230 as the detection result. The abnormal sound detection unit 220 may detect noise that does not easily enter the first output unit 200 and the second output unit 205 and does not reach the user's ear as abnormal sound. As an example, the abnormal sound detection unit 220 may detect a wind noise as the abnormal sound. The wind noise is noise generated when a strong wind strikes the first output unit 200 or the second output unit 205, for example.

  The adjustment unit 230 is connected to the input units 210 and 215 and the abnormal noise detection unit 220, and adjusts the level of the cancellation noise signal output from the cancellation noise signal generation unit 240 according to the detection result of the abnormal noise detection unit 220. To do. When the abnormal noise detection unit 220 detects abnormal noise (for example, when the abnormal noise level exceeds a threshold), the adjustment unit 230 reduces the level of the environmental noise digital signal input to the cancellation noise signal generation unit 240. You may output. Thereby, the adjustment unit 230 can adjust the level of the cancellation noise signal output from the cancellation noise signal generation unit 240. The adjustment unit 230 may adjust the level of a digital signal received from one or both of the two input units 210 and 215 and output the digital signal. The adjustment unit 230 may be provided at any position between the input units 210 and 215 and the first mixer. Here, the level of the signal or environmental noise to be adjusted indicates, for example, the volume, the sound pressure level, or the amplitude, and so on.

  The cancellation noise signal generation unit 240 generates and outputs a cancellation noise signal from the environmental noise digital signals detected by the two or more input units 210 and 215. The cancellation noise signal generation unit 240 may be connected to the adjustment unit 230, invert the phase of the digital signal output from the adjustment unit 230, and generate a cancellation noise signal having an opposite phase to the digital signal. Since the cancellation noise signal generation unit 240 generates a cancellation noise signal from the digital signal whose level has already been adjusted by the adjustment unit 230, the cancellation noise signal generation unit 240 can output a cancellation noise signal having a level corresponding to the detection result of abnormal noise. The cancellation noise signal generation unit 240 may generate a right channel cancellation noise signal and a left channel cancellation noise signal from the environmental noise detected by the input units 210 and 215 having different channels. The cancellation noise signal generation unit 240 may generate a cancellation noise signal common to the right channel and the left channel from the environmental noise detected by one of the input units 210 and 215.

  The first mixer 250 is connected to the output of the cancellation noise signal generation unit 240 and the output of the signal source 110, and mixes the cancellation noise signal from the cancellation noise signal generation unit 240 and the reproduction signal from the signal source 110 (for example, And the mixed signal is output to the first output unit 200 and the second output unit 205. When the mixed signal in which the cancel noise signal is mixed in this manner is output from the first output unit 200 and the second output unit 205, the surrounding environmental noise is combined with the cancel noise signal component and canceled. As a result, the user can only hear the sound of the reproduction signal.

  Next, the abnormal sound detection unit 220 will be described in detail. FIG. 3 shows a block diagram of the abnormal sound detection unit 220. The abnormal sound detection unit 220 includes a second mixer 300, a third mixer 310, a comparison unit 320, and a gain calculation unit 330.

  The second mixer 300 generates an in-phase component of environmental noise detected by two or more inputs 210 and 215. The second mixer 300 is connected to the outputs of the two input units 210 and 215 and mixes digital signals according to environmental noise from the input units 210 and 215 to generate an in-phase component. For example, the second mixer 300 adds the digital signals from the two inputs 210 and 215 to each other without inversion, so that the antiphase components of the two digital signals with respect to each other are substantially canceled and the same. A phase component signal can be generated. Here, since the environmental noise that enters into the first output unit 200 and the second output unit 205 and is subject to noise cancellation is noise that is emitted from a position that is a certain distance away, it is detected by the input units 210 and 215. The sound has almost the same phase. Therefore, the in-phase component generated by the second mixer 300 is in accordance with the environmental noise to be canceled.

  The third mixer 310 generates an antiphase component of the environmental noise detected by the two or more input units 210 and 215. The third mixer 310 is connected to the outputs of the two inputs 210 and 215 and mixes the digital signals from the two inputs 210 and 215 to generate an antiphase component. For example, the third mixer 310 inverts the phase of only one of the digital signals from the two inputs 210 and 215 and adds the two digital signals to each other. As a result, the third mixer 310 can substantially cancel the in-phase components of the digital signals from the input units 210 and 215 with respect to each other, and generate a signal having an anti-phase component. Here, the unusual sound (for example, wind noise) that is difficult to enter the first output unit 200 and the second output unit 205 is noise generated near the input units 210 and 215, and the noise is separated by a certain distance. When detected by the two input units 210 and 215, the sound has different phases. Therefore, the anti-phase component generated by the third mixer 310 corresponds to the abnormal sound.

  The comparison unit 320 compares the in-phase component and the anti-phase component of environmental noise. The comparison unit 320 is connected to the second mixer 300 and the third mixer 310, compares the in-phase component from the second mixer 300 with the anti-phase component from the third mixer 310, and compares the comparison result. You may output. For example, the comparison unit 320 may detect at least one of the presence / absence of abnormal noise and the level of abnormal noise.

  The gain calculation unit 330 is connected to the comparison unit 320 and the adjustment unit 230, and generates a gain setting value used for level adjustment in the adjustment unit 230 according to the comparison result of the comparison unit 320. When the comparison result indicates that the level of abnormal noise exceeds a threshold value (for example, a value of 0 or more), the gain calculation unit 330 decreases the gain setting value, and the abnormal noise level of the comparison result is equal to or lower than the threshold value. If indicated, the gain setpoint may be increased or maintained. For example, the gain setting value may be set in the range of 0 to 1.

  Next, the noise cancellation operation of the active noise cancellation system 100 according to the present embodiment will be described. FIG. 4 shows a flowchart of the noise canceling operation of the active noise canceling system 100 according to the present embodiment.

  First, the noise canceling operation starts in response to the power of the signal processing device 120 being turned on or when the signal processing device 120 detects environmental noise.

  In S410, the input units 210 and 215 detect environmental noise. The input units 210 and 215 generate and output a digital signal corresponding to the environmental noise.

  In S420, the abnormal sound detection unit 220 detects abnormal noise. The abnormal sound detection unit 220 compares the in-phase component from the second mixer 300 and the anti-phase component from the third mixer 310, and outputs a gain setting value corresponding to the comparison result. The abnormal noise detection unit 220 outputs a gain setting value of less than 1 when abnormal noise is detected or the abnormal noise level exceeds the threshold, and when the abnormal noise is not detected or the abnormal noise level is equal to or lower than the threshold. May output a gain setting value of 1.

  The abnormal sound detection unit 220 may set the gain setting value smaller as the level of the signal of the antiphase component of the environmental noise is larger. For example, the comparison unit 320 compares the level of the signal of the antiphase component with respect to the level of the signal of the inphase component (the level of the signal of the antiphase component / the level of the signal of the inphase component) or the difference (the level of the signal of the antiphase component). Level-level of the signal of the in-phase component) is calculated. The gain calculation unit 330 may set the gain setting value smaller as the ratio or difference is larger. Further, the comparison unit 320 compares the level of the antiphase component of the environmental noise with a predetermined threshold value (for example, a value equal to or greater than 0), and detects abnormal noise when the level of the antiphase component is greater than the threshold value. A predetermined gain setting value (for example, a value less than 1) may be set.

  In S430, the adjustment unit 230 adjusts the level of environmental noise according to the presence or absence of abnormal noise detected by the abnormal noise detection unit 220 or the level of abnormal noise. The adjustment unit 230 may adjust and output the environmental noise level according to the gain setting value from the abnormal sound detection unit 220. For example, the adjustment unit 230 may adjust the level by multiplying the level of the environmental noise digital signal from the input units 210 and 215 by a gain setting value. At this time, when the gain setting value = 1 (when the abnormal sound detection unit 220 does not detect the abnormal sound or the abnormal sound level is equal to or lower than the threshold value), the adjustment unit 230 receives the environmental noise digital signal as the input unit 210. And 215 are output at the original level output by 215.

  The adjustment unit 230 may gradually decrease the level of environmental noise when the abnormal noise detected by the abnormal noise detection unit 220 exceeds a threshold value. For example, the adjustment unit 230 may lower the level stepwise to a level defined by the gain setting value in a predetermined period. Further, the adjustment unit 230 may lower the level of environmental noise to a level defined by the gain setting value at a predetermined change rate.

  Further, the adjustment unit 230 may increase the environmental noise level when the abnormal noise level detected by the abnormal noise detection unit 220 becomes lower than the threshold value after decreasing the environmental noise level, and preferably gradually increases the environmental noise level. Raise to. For example, when the abnormal noise detection unit 220 no longer detects abnormal noise, the adjustment unit 230 changes the level of the environmental noise digital signal to the original level output by the input units 210 and 215 during a predetermined period or rate of change. Raise up to. Specifically, the adjustment unit 230 receives the gain setting value = 0.3 and lowers the level of the environmental noise, and then receives the gain setting value = 1, the gain setting value to be used is from 0.3 to 1 It may be increased stepwise at a predetermined period or rate of change. By gradually adjusting the level in this way, the level can be adjusted naturally so as not to give the user more discomfort.

  In S440, the cancellation noise signal generation unit 240 generates and outputs a noise cancellation signal from the environmental noise digital signal from the adjustment unit 230, and the first mixer 250 mixes the reproduction signal and the cancellation noise signal. By outputting the mixed signals from the first output unit 200 and the second output unit 205, the influence of abnormal noise can be suppressed and environmental noise can be canceled. The first mixer 250 mixes the noise cancellation signal generated by the environmental noise from the right channel with the reproduction signal of the right channel, and the noise cancellation signal generated by the environmental noise from the left channel reproduces the left channel. May be mixed with signal.

  In S450, the noise canceling operation ends in response to the signal processing device 120 being turned off or the signal processing device 120 no longer detecting environmental noise. If the environmental noise is further detected without turning off the signal processing device 120, the operation returns to S410.

  The active noise cancellation system 100 according to the present embodiment can reduce the level of the noise cancellation signal when abnormal noise is detected during the ANC operation, and can suppress discomfort to the user.

  Next, a second configuration example of the active noise cancellation system 100 according to the present embodiment will be described. FIG. 5 shows a block diagram of a second configuration example of the active noise cancellation system 100 according to the present embodiment. The description of the configuration substantially the same as the configuration of the active noise cancellation system 100 of the first configuration example shown in FIG. 2 is omitted. The active noise cancellation system 100 of the second configuration example has the same configuration and operation as the active noise cancellation system 100 of the first configuration example. However, the adjustment unit 230 is disposed between the output of the cancellation noise signal generation unit 240 and the input of the first mixer 250.

  The adjustment unit 230 receives the cancellation noise signal output from the cancellation noise signal generation unit 240, and sets the level of the cancellation noise signal according to the presence or absence of abnormal noise detected by the abnormal noise detection unit 220 or the level of abnormal noise. Adjust and output. The adjustment unit 230 may lower the level of the cancellation noise signal, preferably gradually, when the level of the abnormal noise detected by the abnormal noise detection unit 220 exceeds a threshold value. In addition, the adjustment unit 230 may gradually increase the level of the cancellation noise signal when the level of the abnormal noise detected by the abnormal noise detection unit 220 becomes equal to or lower than the threshold after the level of the cancellation noise signal is decreased. Here, the adjustment unit 230 may perform the level adjustment of the cancellation noise signal in the same manner as the environmental noise level adjustment by the adjustment unit 230 of the active noise cancellation system 100 of the first configuration example.

  In the signal processing device 120 of the active noise cancellation system 100 according to the present embodiment, the cancellation noise signal generation unit 240, the abnormal sound detection unit 220, the adjustment unit 230, and the first mixer 250 are digital signal processing. Is to do. The signal processing device 120 can cancel noise more effectively by the noise cancellation processing of the digital configuration. However, the signal processing device 120 of the active noise cancellation system 100 according to the present embodiment may perform analog processing on the analog signal corresponding to the environmental noise from the input units 210 and 215 to perform noise cancellation processing. .

  Further, the signal processing device 120 of the active noise cancellation system 100 according to the present embodiment may not include the first output unit 200 and the second output unit 205, and the first output unit 200 and the second output unit 205 The signal processing device 120 may be externally connected by wire or wireless.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  The order of execution of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior to”. It should be noted that the output can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for convenience, it means that it is essential to carry out in this order. It is not a thing.

DESCRIPTION OF SYMBOLS 100 Active noise cancellation system, 110 Signal source, 120 Signal processing apparatus, 200 1st output part, 205 2nd output part, 210 input part, 215 input part, 220 Abnormal noise detection part, 230 Adjustment part, 240 Cancel noise generation Section, 250 first mixer, 300 second mixer, 310 third mixer, 320 comparison section, 330 gain calculation section

Claims (11)

Two or more inputs for detecting environmental noise, which are respectively arranged in a first output unit and a second output unit of different channels that output sound;
A cancellation noise signal generation unit that generates a cancellation noise signal from the environmental noise detected by the two or more input units;
An abnormal sound detection unit for detecting abnormal noise from the environmental noise detected by the two or more input units;
An adjustment unit that adjusts the level of the cancellation noise signal output from the cancellation noise signal generation unit according to the detection result of the abnormal noise detection unit;
A signal processing apparatus comprising: a first mixer that mixes the cancellation noise signal and the reproduction signal. The abnormal sound detection unit,
A second mixer for generating an in-phase component of the environmental noise detected by the two or more input units;
A third mixer for generating an anti-phase component of the environmental noise detected by the two or more input units;
The signal processing device according to claim 1. The signal processing apparatus according to claim 2, wherein the abnormal sound detection unit includes a comparison unit that compares an in-phase component and an anti-phase component of the environmental noise. The signal processing device according to claim 1, wherein the abnormal sound detection unit detects a wind noise as the abnormal sound. The adjustment unit, when the abnormal sound detection unit detects abnormal noise, the level of the environmental noise input to the cancellation noise signal generation unit or the level of the cancellation noise signal output from the cancellation noise signal generation unit The signal processing device according to any one of claims 1 to 4. The said adjustment part reduces the level of the said environmental noise input into the said cancellation noise signal production | generation part or the level of the said cancellation noise signal according to the level of the abnormal noise which the said abnormal noise detection part detected. Signal processing equipment. The signal processing apparatus according to claim 5, wherein the adjustment unit gradually lowers the level of the environmental noise or the level of the cancellation noise signal input to the cancellation noise signal generation unit. When the level of the ambient noise input to the cancellation noise signal generation unit or the level of the abnormal noise detected by the abnormal noise detection unit after lowering the level of the cancellation noise signal is lower than a threshold, The signal processing apparatus according to claim 5, wherein the level of the environmental noise or the level of the cancellation noise signal input to the cancellation noise signal generation unit is gradually increased. The two or more input units convert input environmental noise into a digital signal,
The cancel noise signal generation unit, the abnormal sound detection unit, the adjustment unit, and the first mixer perform digital signal processing on the digital signal. The signal processing apparatus as described. The signal processing apparatus according to claim 1, comprising the first output unit and the second output unit. A signal processing device according to any one of claims 1 to 10,
A signal source for supplying a reproduction signal;
Active noise cancellation system with

Images