Acoustic processing method, acoustic processing system, and program

Abstract

This sound processing system comprises: a signal acquisition unit which acquires a first sound signal that shows a sound received by a sound reception device; and a sound processing unit which rotates, concurrently with the reception of the sound, the phase of the first sound signal in one direction with the passage of time, and generates a second sound signal.

Description

[Technical field]

[0001] The present disclosure relates to techniques for processing acoustic signals. [Background technology]

[0002] Techniques for suppressing feedback that occurs in an acoustic system including a sound collection device and a sound emission device have been proposed in the past. For example, Patent Document 1 discloses a technique for suppressing feedback using a notch filter that suppresses acoustic components in a stop band of an acoustic signal. In the technique of Patent Document 1, a frequency that causes feedback (hereinafter referred to as a "feedback frequency") is estimated by analyzing an acoustic signal, and a frequency band including the frequency is set as the stop band of a notch filter. Patent Document 2 discloses a technique for suppressing feedback by changing the pitch of an acoustic signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-138329 A [Patent Document 2] JP 2012-124826 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technology of Patent Document 1, it is necessary to identify the howling frequency by analyzing the acoustic signal. Therefore, there is a problem that the configuration and processing for suppressing the howling become complicated. In consideration of the above circumstances, one aspect of the present disclosure aims to suppress the howling without the need to identify the howling frequency and without changing the auditory perceptible characteristics (e.g., pitch) of the acoustic signal. [Means for solving the problem]

[0005] In order to solve the above problems, an acoustic processing method according to one embodiment of the present disclosure acquires a first acoustic signal representing sound picked up by a sound collection device, and generates a second acoustic signal by rotating the phase of the first acoustic signal in one direction over time in parallel with the sound collection.

[0006] An acoustic processing system according to one embodiment of the present disclosure includes a signal acquisition unit that acquires a first acoustic signal representing sound picked up by a sound collection device, and an acoustic processing unit that generates a second acoustic signal by rotating the phase of the first acoustic signal in one direction over time in parallel with the sound collection.

[0007] A program according to one embodiment of the present disclosure causes a computer to function as a signal acquisition unit that acquires a first acoustic signal representing sound picked up by a sound collection device, and an acoustic processing unit that generates a second acoustic signal by rotating the phase of the first acoustic signal in one direction over time in parallel with the sound collection. [Brief description of the drawings]

[0008] [Figure 1] 1 is a block diagram illustrating a configuration of a sound processing system according to a first embodiment. [Diagram 2] FIG. 2 is a block diagram illustrating an example of a functional configuration of the sound processing system. [Diagram 3] FIG. 11 is an explanatory diagram of a phase shift process. [Figure 4] 3 is a block diagram illustrating a specific configuration of an acoustic processing unit. FIG. [Diagram 5] 11 is a flowchart illustrating a specific procedure of a phase shifting process. [Figure 6] FIG. 11 is a block diagram illustrating a specific configuration of a sound processing unit in a modified example. [Figure 7] FIG. 11 is a block diagram of an acoustic processing unit in a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A: First embodiment 1 is a block diagram illustrating a configuration of a sound processing system 100 according to a first embodiment of the present disclosure. The sound processing system 100 is a loudspeaker system that collects sound (hereinafter referred to as "target sound") produced by a specific sound source, adjusts the volume of the target sound, and then plays it back. The target sound is any sound, such as a voice or a musical sound. The sound processing system 100 includes a sound collection device 10, a sound emission device 20, and a signal processing device 30.

[0010] The sound collection device 10 is a microphone that generates an audio signal x by collecting surrounding sounds. The audio signal x is a time domain signal that represents the waveform of the sound collected by the sound collection device 10. The signal processing device 30 generates an audio signal z from the audio signal x generated by the sound collection device 10. The signal processing device 30 generates the audio signal z in parallel with the sound collection by the sound collection device 10. The sound emission device 20 (e.g., a speaker) reproduces the sound represented by the audio signal z generated by the signal processing device 30. Note that communication between the signal processing device 30 and the sound collection device 10, or communication between the signal processing device 30 and the sound emission device 20 may be either wired communication or wireless communication. In addition, one or both of the sound collection device 10 and the sound emission device 20 may be mounted on the signal processing device 30.

[0011] The sound collection device 10 and the sound emission device 20 are installed in one acoustic space. Therefore, a part of the sound reproduced by the sound emission device 20 (hereinafter referred to as "reproduced sound") reaches the sound collection device 10 after being reflected by, for example, the wall surface of the acoustic space. That is, the acoustic signal x includes an acoustic component of the target sound that is the original purpose of sound collection, as well as an acoustic component of the sound that arrives at the sound collection device 10 directly or indirectly from the sound emission device 20 (hereinafter referred to as "feedback sound"). In a closed-loop acoustic system in which the feedback sound from the sound emission device 20 reaches the sound collection device 10 as described above, if the gain of the entire acoustic system exceeds 1 and the phases of the target sound and the feedback sound are the same or similar, there is a possibility that howling will occur. The signal processing device 30 functions as a howling suppression device that generates an acoustic signal z by executing a process for preventing howling on the acoustic signal x.

[0012] The signal processing device 30 includes a control device 31, a storage device 32, an operation device 33, an A / D converter 34, a D / A converter 35, and an amplifier 36. The signal processing device 30 is realized by, for example, a portable information device such as a smartphone or a tablet terminal, or a portable or stationary information device such as a personal computer. The signal processing device 30 may be realized by a single device, or may be realized by a plurality of devices configured separately from each other.

[0013] The control device 31 is composed of one or more processors that control each element of the signal processing device 30. Specifically, the control device 31 is composed of one or more types of processors, such as a CPU (Central Processing Unit), an SPU (Sound Processing Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or an ASIC (Application Specific Integrated Circuit).

[0014] The storage device 32 is one or more memories that store the programs executed by the control device 31 and the data used by the control device 31. The storage device 32 is configured with a known recording medium such as a magnetic recording medium or a semiconductor recording medium. The storage device 32 may be configured with a combination of a plurality of types of recording media. Also, a portable recording medium that can be attached to and detached from the signal processing device 30, or an external recording medium (e.g., online storage) with which the signal processing device 30 can communicate may be used as the storage device 32.

[0015] The operation device 33 is an input device that accepts operations by a user of the sound processing system 100. For example, a plurality of operators that can be operated by a user, or a touch panel that detects a touch by a player to a display surface of a display device (not shown) is used as the operation device 33.

[0016] The A / D converter 34 converts the analog acoustic signal x supplied from the sound collection device 10 into a digital acoustic signal X1. The acoustic signal X1 is expressed as a time series of samples arranged on a time axis. The control device 31 generates a digital acoustic signal Z from the acoustic signal X1. The acoustic signal X1 is an example of a "first acoustic signal."

[0017] The D / A converter 35 converts the acoustic signal Z into an analog acoustic signal z. The amplifier 36 amplifies the acoustic signal z. The gain of the amplifier 36 is set, for example, according to an instruction from a user via the operation device 33. The acoustic signal z amplified by the amplifier 36 is supplied to the sound emitting device 20, whereby the sound emitting device 20 reproduces the sound represented by the acoustic signal z. Note that the amplifier 36 (digital amplifier) ​​installed in the stage preceding the D / A converter 35 may amplify the digital acoustic signal Z. The acoustic signal Z is an example of a "second acoustic signal."

[0018] 2 is a block diagram illustrating a functional configuration of the signal processing device 30. The control device 31 executes a program stored in the storage device 32 to function as an acoustic processing unit 50. The acoustic processing unit 50 processes an acoustic signal X1 to generate an acoustic signal Z. The processing by the acoustic processing unit 50 (hereinafter referred to as "phase shift processing") is performed in parallel with sound collection by the sound collection device 10 and sound reproduction by the sound emission device 20.

[0019] FIG. 3 is an explanatory diagram of the phase shift processing executed by the sound processing unit 50. The sound processing unit 50 generates the sound signal Z by phase shift processing that rotates the phase of the sound signal X1 in one direction over time. That is, the phase difference of the sound signal Z with respect to the sound signal X1 changes moment by moment over time. The phase difference of the sound signal Z is the difference between the phase of the sound signal X1 and the phase of the sound signal Z. Specifically, a cycle is repeated in which the phase difference of the sound signal Z with respect to the sound signal X1 increases over time from 0° to 360°. The sound processing unit 50 supplies the sound signal Z after the phase shift processing to the D / A converter 35. As can be understood from the above description, the sound processing unit 50 generates the sound signal Z by rotating the phase of the sound signal X1 in one direction over time in parallel with the sound collection by the sound collection device 10, and causes the sound emitting device 20 to reproduce the sound represented by the sound signal Z.

[0020] When the delay amount in the closed loop system of the sound processing system 100 of the sound component repeatedly circulates is close to or coincides with an integer multiple of the period of the sound component, the condition for howling is met. According to the first embodiment, even if the condition for howling is met, the phase of the sound component circulating in the closed loop system is dispersed, and as a result, the occurrence of standing waves is suppressed. That is, the phase shift process imparts a time-varying phase difference between the sound component of the target sound in the sound signal X1 and the sound component of the feedback sound that returns in the same phase as the target sound component. Therefore, the howling caused by the feedback sound from the sound emitting device 20 to the sound collecting device 10 can be suppressed without requiring a configuration and process for identifying the howling frequency. In addition, since it is not necessary to change the frequency of the sound signal X1, the howling can be suppressed without changing the auditory perceptible characteristics (for example, pitch or sound quality) of the sound reproduced by the sound emitting device 20.

[0021] 3, the acoustic processing unit 50 of the first embodiment rotates the phase of the acoustic signal X1 across the entire frequency band at a constant speed (hereinafter referred to as the "rotation speed") R. Specifically, for example, the phase of the acoustic signal Z changes at a constant rotation speed R across the entire audible band B from 20 Hz to 20 kHz.

[0022] Moreover, the phase difference of the acoustic signal Z relative to the acoustic signal X1 is maintained equal across the entire frequency band. Therefore, the phase difference of the acoustic signal Z relative to the acoustic signal X1 is equal within the audible band B. With the above configuration, since the group delay does not change between the acoustic signal X1 before the phase-shift processing and the acoustic signal Z after the phase-shift processing, the waveform of the acoustic signal Z (e.g., the envelope on the time axis) does not substantially change from the acoustic signal X1 before the phase-shift processing. Therefore, howling can be suppressed without changing the auditory perceptible characteristics (e.g., pitch or sound quality) of the sound reproduced by the sound emitting device 20.

[0023] However, when the phase of the audio signal X1 is rotated at an excessively fast speed, the waveform of the audio signal Z may suffer from significant distortion (hereinafter referred to as "waveform distortion") that is audibly perceptible, compared to the audio signal X1 before phase shift processing. As a result of testing by the inventors, it was confirmed that when the phase rotation speed R is set to 2 rotations per second (720° / second) or less, there is a tendency that the waveform distortion caused by the phase rotation is difficult to audibly perceive. Based on the above findings, in the first embodiment, the phase rotation speed R by the audio processing unit 50 is set to 2 rotations per second or less, and more preferably 1.5 rotations per second or less. With the above configuration, howling can be suppressed while suppressing the manifestation of waveform distortion caused by phase rotation.

[0024] On the other hand, when the phase of the acoustic signal X1 is rotated at an excessively slow speed, the phase dispersion between the acoustic components circulating in the closed loop system is suppressed. Therefore, there is a possibility that the howling caused by the feedback sound cannot be effectively suppressed. As a result of the test by the inventor, it was confirmed that the howling can be effectively suppressed by setting the phase rotation speed R to 0.01 rotations per second (3.6° / second) or more. Based on the above findings, in the first embodiment, the phase rotation speed R by the acoustic processing unit 50 is set to 0.01 rotations per second or more, and more preferably to 0.1 rotations per second or more. According to the above configuration, the howling caused by the feedback sound from the sound emitting device 20 to the sound collecting device 10 can be effectively suppressed.

[0025] As can be understood from the above description, in the first embodiment, the rotation speed R is set to 0.01 rotations per second or more and 2 rotations per second or less. In a more preferred embodiment, the rotation speed R is set to 0.1 rotations per second or more and 1.5 rotations per second or less. In an even more preferred embodiment, the rotation speed R is set to 1 rotation per second (360° / sec).

[0026] Fig. 4 is a block diagram illustrating a specific configuration of the acoustic processing unit 50. The acoustic processing unit 50 of the first embodiment includes a phase shift unit 51, a synthesis unit 52, and a setting unit 53. The configuration illustrated in Fig. 4 is an example of the configuration of the acoustic processing unit 50. In the following description, a time-domain phase-shifting process is illustrated as an example, but the phase-shifting process may be a frequency-domain signal processing.

[0027] The phase shift unit 51 generates an acoustic signal Y1 by processing the acoustic signal X1. The acoustic signal Y1 is a signal having a different phase from the acoustic signal X1. Specifically, the phase shift unit 51 generates the acoustic signal Y1 by performing a Hilbert transform on the acoustic signal X1. Therefore, the acoustic signal Y1 is a signal whose phase is delayed by 90° with respect to the acoustic signal X1. The Hilbert transform on the acoustic signal X1 is realized by, for example, an FIR (Finite Impulse Response) filter. As can be understood from the above explanation, two systems of acoustic signals (X1, Y1) having different phases are supplied to the synthesis unit 52. The acoustic signal Y1 is an example of a "third acoustic signal."

[0028] The synthesis unit 52 generates an audio signal Z by synthesizing the audio signal X1 and the audio signal Y1. Specifically, the synthesis unit 52 generates the audio signal Z by a weighted sum of the audio signal X1 and the audio signal Y1. The synthesis unit 52 of the first embodiment includes an adjustment unit 521, an adjustment unit 522, and an addition unit 523. The adjustment unit 521 is a multiplier that generates an audio signal X2 by multiplying the audio signal X1 by a weight value αx. The adjustment unit 522 is a multiplier that generates an audio signal Y2 by multiplying the audio signal Y1 by a weight value αy. The addition unit 523 generates an audio signal Z by adding the audio signal X2 and the audio signal Y2. As can be understood from the above description, the weight value αx and the weight value αy are the mixing ratio of the audio signal X1 and the audio signal Y1. The audio signal X2 is an example of a "fourth audio signal", and the audio signal Y2 is an example of a "fifth audio signal".

[0029] The setting unit 53 controls the weighting value αx and the weighting value αy. Specifically, the setting unit 53 sets each of the weighting value αx and the weighting value αy to a value within a range of -1 or more and +1 or less. By appropriately setting the mixing ratio (αx, αy) of the two systems of acoustic signals (X1, Y1) having different phases, the synthesis unit 52 can generate an acoustic signal Z having an arbitrary phase difference with respect to the acoustic signal X1. For example, by setting the weighting value αx to a value within a range of 0 or more and +1 or less, and setting the weighting value αy to a value within a range of -1 or more and 0 or less, an acoustic signal Z having a phase difference set to 0° or more and 90° or less with respect to the acoustic signal X1 is generated. In addition, by setting the weighting value αx to a value within a range of -1 or more and 0 or less, and setting the weighting value αy to a value within a range of -1 or more and 0 or less, an acoustic signal Z having a phase difference set to 90° or more and 180° or less with respect to the acoustic signal X1 is generated. By setting the weighting value αx to a value between -1 and 0, and setting the weighting value αy to a value between 0 and +1, an acoustic signal Z is generated whose phase difference with respect to the acoustic signal X1 is set to 180° to 270°. By setting the weighting value αx to a value between 0 and +1, and setting the weighting value αy to a value between 0 and +1, an acoustic signal Z is generated whose phase difference with respect to the acoustic signal X1 is set to 270° to 360°. Note that the phase difference between the acoustic signals X1 and Y1 is not limited to 90°.

[0030] The setting unit 53 changes each of the weighting value αx and the weighting value αy over time in parallel with the sound collection by the sound collection device 10. The phase rotation speed R of the sound signal Z depends on the change speed of the weighting value αx and the weighting value αy. Specifically, the phase rotation speed R increases as the change speed of the weighting value αx and the weighting value αy increases. As described above, the setting unit 53 of the first embodiment changes each of the weighting value αx and the weighting value αy over time so that the phase of the sound signal Z rotates at a rotation speed R within a range of 0.01 rotations per second or more and 2 rotations per second or less. As described above, the phase difference of the sound signal Z with respect to the sound signal X1 changes by controlling the mixture ratio (αx, αy) of the sound signal X1 and the sound signal Y1. Therefore, according to the first embodiment, howling can be suppressed by a simple configuration and processing.

[0031] 5 is a flowchart illustrating a specific procedure of the phase-shifting process executed by the control device 31. For example, the phase-shifting process is started in response to an instruction from a user via the operation device 33. The phase-shifting process is continued in parallel with the sound collection by the sound collection device 10.

[0032] When the phase shift process is started, the control device 31 acquires the acoustic signal X1 from the A / D converter 34 (S1). That is, the control device 31 functions as a signal acquisition unit that acquires the acoustic signal X1. The control device 31 (acoustic processing unit 50) generates the acoustic signal X from the acoustic signal X1 in the following procedure (S2 to S6).

[0033] The phase shift unit 51 generates an acoustic signal Y1 having a phase different from that of the acoustic signal X1 from the acoustic signal X1 (S2). The setting unit 53 updates the weighting value αx and the weighting value αy (S3). Specifically, the setting unit 53 changes the weighting value αx and the weighting value αy by an amount of change set so that the phase rotation speed R of the acoustic signal Z becomes a target value (0.01≦R≦2). The adjustment unit 521 generates an acoustic signal X2 by multiplying the acoustic signal X1 by the updated weighting value αx (S4), and the adjustment unit 522 generates an acoustic signal Y2 by multiplying the acoustic signal Y1 by the updated weighting value αy (S5). The synthesis unit 52 generates an acoustic signal Z by adding the acoustic signal Y1 and the acoustic signal Y2 (S6). The synthesis unit 52 outputs the acoustic signal Z to the D / A converter 35 (S7).

[0034] The control device 31 determines whether a predetermined end condition is met (S8). The end condition is, for example, when a user issues an end command via an operation on the operation device 33, or when the supply of the acoustic signal X1 from the sound collection device 10 is stopped. If the end condition is not met (S8: NO), the control device 31 shifts the process to step S1. That is, acquisition of the acoustic signal X1 (S1), generation of the acoustic signal Z (S2-S6), and output of the acoustic signal Z (S7) are repeated in parallel with the sound collection by the sound collection device 10. On the other hand, if the end condition is met (S8: YES), the control device 31 ends the phase shift process.

[0035] B: Second embodiment The second embodiment will be described below. In the first embodiment, a form in which the rotation speed R of the phase is fixed to a predetermined value is exemplified. In the second embodiment, the rotation speed R is variably controlled. Note that, for elements in each configuration exemplified below that have the same functions as those in the first embodiment, the reference symbols used in the description of the first embodiment are used and detailed descriptions of each are omitted as appropriate.

[0036] The user operates the operation device 33 to instruct the signal processing device 30 on the rotation speed R. Specifically, the user adjusts the rotation speed R by operating the operation device 33 while listening to the sound reproduced by the sound emitting device 20 in parallel with the sound collection by the sound collection device 10. For example, the rotation speed R is adjusted so that waveform distortion does not become apparent in the sound reproduced by the sound emitting device 20 and howling does not occur.

[0037] The setting unit 53 receives an instruction for the rotation speed R from the user. The setting unit 53 controls the rate of change of each of the weighting values ​​αx and αy so that the phase of the sound signal Z rotates at the rotation speed R instructed by the user. For example, the setting unit 53 sets the amount of change of the weighting values ​​αx and αy in step S3 of Fig. 5 according to the rotation speed R instructed by the user.

[0038] The second embodiment also achieves the same effects as the first embodiment. Moreover, in the second embodiment, since the phase rotation speed R of the acoustic signal Z is changed, howling can be effectively suppressed in various environments with different acoustic characteristics such as reflection characteristics.

[0039] C: Modification Specific modified embodiments added to each of the above-mentioned embodiments are exemplified below. Two or more embodiments selected from the following examples may be appropriately combined as long as they are not mutually contradictory.

[0040] (1) The configuration of the acoustic processing unit 50 is not limited to the configuration exemplified in Fig. 4. For example, an acoustic signal Z may be generated from an acoustic signal X1 by an acoustic processing unit 50 exemplified in Fig. 6. The acoustic processing unit 50 in Fig. 6 includes a phase shift unit 54 in addition to the same elements as those in the first embodiment (a phase shift unit 51, a synthesis unit 52, and a setting unit 53).

[0041] 6 generates an acoustic signal Y1 by changing the phase of the acoustic signal X1. The acoustic signal Y1 is a signal in which the phase of the acoustic signal X1 is shifted (e.g., delayed) by a predetermined amount δy. The acoustic signal Y1 is an example of a "third acoustic signal."

[0042] The phase shift unit 54 processes the acoustic signal X1 to generate an intermediate signal W. The intermediate signal W is an acoustic signal obtained by changing (e.g., delaying) the phase of the acoustic signal X1 by a predetermined amount δx. Specifically, the amount of phase shift δy by the phase shift unit 51 and the amount of phase shift δx by the phase shift unit 54 are set so that the phase difference between the acoustic signal Y1 and the intermediate signal W is 90°. As can be understood from the above explanation, the phase shift unit 54 changes the phase of the acoustic signal X1 to generate an intermediate signal W having a predetermined phase difference with respect to the acoustic signal Y1. Note that a configuration in which the amount of phase shift δy is set to 90° and the amount of phase shift δx is set to 0° corresponds to the configuration in FIG. 4.

[0043] The synthesis unit 52 generates the audio signal Z by synthesizing the intermediate signal W and the audio signal Y1. Specifically, the synthesis unit 52 generates the audio signal Z by a weighted sum of the intermediate signal W and the audio signal Y1. The synthesis unit 52 of the first embodiment includes an adjustment unit 521, an adjustment unit 522, and an addition unit 523. The adjustment unit 521 is a multiplier that generates an audio signal X2 by multiplying the intermediate signal W by a weight value αx. The adjustment unit 522 is a multiplier that generates an audio signal Y2 by multiplying the audio signal Y1 by a weight value αy. The addition unit 523 generates the audio signal Z by adding the audio signal X2 and the audio signal Y2. As can be understood from the above description, the weight value αx and the weight value αy are the mixing ratio of the intermediate signal W and the audio signal Y1. The audio signal X2 is an example of a "fourth audio signal", and the audio signal Y2 is an example of a "fifth audio signal".

[0044] As in the first embodiment, the setting unit 53 changes each of the weighting value αx and the weighting value αy over time in parallel with the sound collection by the sound collection device 10. Specifically, the setting unit 53 changes each of the weighting value αx and the weighting value αy over time so that the phase of the acoustic signal Z rotates at a rotation speed R within a range of 0.01 rotations per second or more and 2 rotations per second or less. Therefore, the same effect as in the first embodiment is realized in this modified example. Moreover, according to the configuration of FIG. 6, howling can be effectively suppressed by a simple configuration and processing for changing each of the weighting value αx and the weighting value αy.

[0045] (2) In each of the above-described embodiments, the phase of the acoustic signal Z changes at a constant rotation speed R across the entire audible band B. However, the rotation speed R may be different for each of a plurality of frequency bands on the frequency axis.

[0046] Fig. 7 is a block diagram of an acoustic processing unit 50A in this modified example. The acoustic processing unit 50 in each of the above-described embodiments is replaced with the acoustic processing unit 50A in Fig. 7. The acoustic processing unit 50A includes a band splitting unit 55, N signal processing units U-1 to UN (N is a natural number equal to or greater than 2), a signal mixing unit 56, and a setting unit 53.

[0047] The band division unit 55 generates N band signals X1-1 to X1-N from the audio signal X1. Each band signal X1-n (n=1 to N) is an audio signal that represents an audio component in a frequency band Bn of the audio signal X1. The frequency band Bn is one of N different frequency bands B-1 to BN in the audible band B.

[0048] Each signal processing unit Un generates an audio signal Zn by phase shift processing that rotates the phase of the band signal X1-n in one direction over time, similar to the audio processing unit 50 in each of the above-mentioned embodiments. Specifically, the signal processing unit Un includes a phase shift unit 51 that generates a band signal Y1-n from the band signal Xn, and a synthesis unit 52 that generates an audio signal Zn by a weighted sum of the band signal X1-n and the band signal Y1-n. The synthesis unit 52 of the signal processing unit Un generates an audio signal Z1-n by adding the band signal X1-n weighted by the weight value αx-n and the band signal Y1-n weighted by the weight value αy-n. Note that the audio processing unit 50 illustrated in FIG. 6 may be adopted as each signal processing unit Un.

[0049] The setting unit 53 sets a weighting value αx-n and a weighting value αy-n for each of the N signal processing units U-1 to UN. Specifically, the setting unit 53 changes each weighting value αx-n and each weighting value αy-n over time so that the phases of the N acoustic signals Z-1 to ZN rotate at different rotation speeds R. The rotation speed R in each signal processing unit Un is set to a value within a range of 0.01 rotations per second or more and 2 rotations per second or less.

[0050] The signal mixer 56 mixes (e.g., adds) N acoustic signals Z-1 to ZN generated by different signal processors Un to generate an acoustic signal Z. According to the configuration in Fig. 7, the rotation speeds R in the acoustic signals Zn are different, and therefore the effect of suppressing feedback is particularly remarkable.

[0051] In addition, according to each of the above-mentioned embodiments in which the rotation speed R is constant over the entire audible band B, there is an advantage that the configuration and processing of the acoustic processing unit 50 are simplified compared to the configuration of Fig. 7 in which the rotation speed R differs for each frequency band Bn. In addition, in the configuration of Fig. 7 in which the rotation speed R differs for each frequency band Bn, the phase difference becomes discontinuous near the boundary between adjacent frequency bands Bn on the frequency axis, so there is a possibility that the sound quality of the reproduced sound by the sound emitting device 20 will deteriorate. In each of the above-mentioned embodiments, the phase difference is the same over the entire audible band B, and the rotation speed R is also constant, so there is an advantage that deterioration in the sound quality of the reproduced sound caused by discontinuity in the phase difference can be suppressed.

[0052] (3) In each of the above-described embodiments, the acoustic signal Z is generated by rotating the phase of the acoustic signal X1 in one direction, but the direction in which the phase of the acoustic signal X1 is rotated is not limited to a specific direction (e.g., an increasing direction). For example, the acoustic processing unit 50 may generate the acoustic signal Z by increasing the phase of the acoustic signal X1 in a first period on the time axis and decreasing the phase of the acoustic signal X1 in a second period different from the first period. Also, it is not necessarily necessary to rotate the phase of the acoustic signal X1 one rotation. For example, the phase may be moved back and forth within a predetermined range.

[0053] (4) In each of the above embodiments, the phase of the acoustic signal X1 is rotated over the entire audible frequency band B, but it is also possible to assume a configuration in which the phase is not rotated for a specific frequency band. For example, it is possible to assume a configuration in which the phase is not rotated for a frequency band in which feedback is unlikely to occur.

[0054] 7, for example, the signal processing unit Un corresponding to the frequency band Bn in which feedback is unlikely to occur among the N frequency bands B-1 to BN in the audible band B does not execute phase-shift processing. That is, the signal processing unit Un outputs the acoustic signal X1-n as the acoustic signal Zn without processing it. According to the above configuration, the phase-shift processing is executed only for the frequency band Bn in which feedback is a problem, so that waveform distortion of the reproduced sound can be suppressed compared to a form in which the phase of the acoustic signal X1 is rotated over the entire audible band B.

[0055] (5) In the above-described embodiments, the phase rotation is steadily continued, but the process of rotating the phase of the acoustic signal X1 may be limited to a specific period on the time axis (hereinafter, referred to as the "processing period"). During periods other than the processing period, the acoustic signal X1 may be output from the acoustic processing unit 50 as the acoustic signal Z.

[0056] (6) The signal processing device 30 may be realized by a server device that communicates with an information device such as a smartphone or a tablet terminal. For example, an acoustic signal X1 representing the sound collected by the sound collection device 10 is transmitted from the terminal device to the information processing device. The acoustic processing unit 50 of the signal processing device 30 generates an acoustic signal Z from the acoustic signal X1 by phase shift processing similar to that of each of the above-mentioned embodiments, and transmits the acoustic signal Z to the information device. The information device reproduces the sound represented by the acoustic signal Z received from the signal processing device 30. The above configuration also achieves the same effects as each of the above-mentioned embodiments.

[0057] (7) As described above, the function (sound processing unit 50) of the signal processing device 30 according to each of the above-mentioned embodiments is realized by the cooperation of one or more processors constituting the control device 31 and the program stored in the storage device 32. The program according to the present disclosure can be provided in a form stored in a computer-readable recording medium and installed in a computer. The recording medium is, for example, a non-transitory recording medium, and a good example is an optical recording medium (optical disk) such as a CD-ROM, but also includes any known type of recording medium such as a semiconductor recording medium or a magnetic recording medium. Note that the non-transitory recording medium includes any recording medium except for a transient, propagating signal, and does not exclude volatile recording media. In addition, in a configuration in which a distribution device distributes a program via a communication network, the recording medium that stores the program in the distribution device corresponds to the non-transitory recording medium described above.

[0058] D: Notes From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0059] A sound processing method according to one aspect (aspect 1) of the present disclosure acquires a first sound signal representing sound collected by a sound collection device, and generates a second sound signal by rotating the phase of the first sound signal in one direction over time in parallel with the sound collection. According to the above aspect, the second sound signal is generated by rotating the phase of the first sound signal representing the sound collected by the sound collection device in one direction over time. That is, the phase is distributed between sound components that repeatedly circulate in a closed loop system including a sound emission device and a sound collection device to which feedback sound from the sound emission device reaches. Therefore, howling caused by feedback sound from the sound emission device to the sound collection device can be suppressed without requiring a configuration and processing for identifying the howling frequency. In addition, since it is not necessary to change the frequency of the sound signal, howling can be suppressed without changing the auditory perceptible characteristics (e.g., pitch or sound quality) of the sound reproduced by the sound emission device.

[0060] The condition for rotating the phase of the first acoustic signal is arbitrary. For example, the direction of phase rotation may be either a direction in which the phase increases or a direction in which the phase decreases. Also, the speed of phase rotation may be either a fixed value or a variable value. For example, the phase of the second acoustic signal changes stepwise or continuously (for example, linearly or curvilinearly).

[0061] It is not necessary that the phase of the second acoustic signal rotates under equal conditions throughout the entire audible band on the frequency axis. For example, in addition to the form (aspect 6) in which the phase of the first acoustic signal rotates while maintaining an equal phase difference within the audible band, a form in which the phase of the acoustic signal differs for each frequency band set on the frequency axis is also assumed. In addition to the form (aspect 5) in which the phase of the acoustic signal rotates at an equal speed within the audible band, a form in which the phase of the acoustic signal rotates at a different speed for each frequency band set on the frequency axis is also assumed.

[0062] In the specific example (Aspect 2) of Aspect 1, the sound represented by the second sound signal is further reproduced by the sound emitting device. In a configuration in which a part of the sound represented by the second sound signal is fed back from the sound emitting device to the sound collecting device, feedback is likely to become evident. Therefore, the suppression of feedback according to the present disclosure is effective.

[0063] In a specific example (Aspect 3) of Aspect 1 or Aspect 2, the phase rotation speed is 2 rotations per second or less. If the phase of an acoustic signal is rotated at an excessively fast speed, significant waveform distortion that can be audibly perceived may occur in the acoustic signal. According to an embodiment in which the phase rotation speed is set to 2 rotations per second (720° / sec) or less, howling can be suppressed while suppressing the manifestation of waveform distortion caused by phase rotation.

[0064] In a specific example (Aspect 4) of any one of Aspects 1 to 3, the phase rotation speed is 0.01 rotations per second or more. In an embodiment in which the phase of an acoustic signal is rotated at an excessively slow speed, there is a possibility that howling cannot be effectively suppressed. According to an embodiment in which the phase rotation speed is set to 0.01 rotations per second (3.6° / sec) or more, howling can be effectively suppressed.

[0065] In a specific example (Aspect 5) of any one of Aspects 1 to 4, in generating the second acoustic signal, a third acoustic signal is generated by changing the phase of the first acoustic signal, a fourth acoustic signal is generated by multiplying the first acoustic signal by a first weighting value, and a fifth acoustic signal is generated by multiplying the third acoustic signal by a second weighting value is added to generate the second acoustic signal, and the phase of the first acoustic signal is rotated by changing each of the first weighting value and the second weighting value over time. According to the above aspect, howling can be effectively suppressed by a simple configuration and processing for changing each of the first weighting value and the second weighting value.

[0066] In a specific example (Aspect 6) of any of Aspects 1 to 4, in generating the second acoustic signal, a third acoustic signal is generated by changing the phase of the first acoustic signal, an intermediate signal having a predetermined phase difference with respect to the third acoustic signal is generated by changing the phase of the first acoustic signal, a fourth acoustic signal is generated by multiplying the intermediate signal by a first weighting value, and a fifth acoustic signal is generated by multiplying the third acoustic signal by a second weighting value is added to generate the second acoustic signal, and the phase of the first acoustic signal is rotated by changing each of the first weighting value and the second weighting value over time. According to the above aspect, howling can be effectively suppressed by a simple configuration and processing for changing each of the first weighting value and the second weighting value.

[0067] In a specific example (Aspect 7) of any one of Aspects 1 to 6, the phase of the first acoustic signal is rotated at a constant speed within the audible band. In the above aspects, since the phase of the first acoustic signal is rotated at a constant speed within the audible band, the configuration and processing are simplified compared to a configuration in which the phase is rotated at different speeds for each frequency band on the frequency axis. The audible band is, for example, a frequency band from 20 Hz to 20 kHz.

[0068] In a specific example (Aspect 8) of Aspect 7, the phase difference between the second acoustic signal and the first acoustic signal is equal within the audible band. In the above aspect, the group delay of the acoustic signal does not change before and after the phase rotation, so the waveform (e.g., envelope waveform) of the acoustic signal does not substantially change before and after the processing. Therefore, howling can be suppressed without changing the auditory perceptible characteristics (e.g., pitch or sound quality) of the sound reproduced by the sound emitting device.

[0069] In a specific example (Aspect 9) of any one of Aspects 1 to 4, the second acoustic signal is generated by generating a plurality of band signals having different frequency bands from the first acoustic signal, rotating each of the plurality of band signals at a different rotation speed, and mixing the plurality of band signals after the rotation to generate the second acoustic signal. According to the above aspect, since the rotation angle differs for each frequency band, howling can be effectively suppressed compared to a configuration in which the rotation angle is constant across the entire audible band.

[0070] In a specific example of any one of aspects 1 to 9, in generating the second acoustic signal, a third acoustic signal is generated by changing the phase of the first acoustic signal, the second acoustic signal is generated by mixing the first acoustic signal and the third acoustic signal, and the phase is rotated by changing the mixing ratio of the first acoustic signal and the third acoustic signal. In the above aspects, the phase of the second acoustic signal can be rotated by a simple configuration and processing that changes the mixing ratio of the first acoustic signal and the third acoustic signal, which have different phases.

[0071] An acoustic processing system according to one embodiment (embodiment 10) of the present disclosure includes a signal acquisition unit that acquires a first acoustic signal representing sound picked up by a sound collection device, and an acoustic processing unit that generates a second acoustic signal by rotating the phase of the first acoustic signal in one direction over time in parallel with the sound collection.

[0072] A program according to one embodiment (embodiment 11) of the present disclosure causes a computer to function as a signal acquisition unit that acquires a first acoustic signal representing sound picked up by a sound collection device, and an acoustic processing unit that generates a second acoustic signal by rotating the phase of the first acoustic signal in one direction over time in parallel with the sound collection. [Explanation of symbols]

[0073] 100...acoustic processing system, 10...sound collection device, 20...sound emission device, 30...signal processing device, 31...control device, 32...storage device, 33...operation device, 34...A / D converter, 35...D / A converter, 36...amplifier, 50...acoustic processing unit, 51...phase shift unit, 52...synthesizing unit, 521...adjustment unit, 522...adjustment unit, 523...addition unit, 53...setting unit, 55...band division unit, 56...signal mixing unit, U-1 to UN...signal processing unit.

Claims

1. A first sound signal representing a sound collected by a sound collection device is obtained; A second acoustic signal is generated by rotating the phase of the first acoustic signal in one direction over time in parallel with the sound collection.

1. A computer-implemented method for audio processing, comprising: In generating the second acoustic signal, generating a third acoustic signal by varying a phase of the first acoustic signal; generating the second acoustic signal by adding a fourth acoustic signal generated by multiplying the first acoustic signal by a first weighting value and a fifth acoustic signal generated by multiplying the third acoustic signal by a second weighting value; The phase of the first acoustic signal is rotated by varying each of the first weighting value and the second weighting value over time. Acoustic processing methods.

2. A first sound signal representing a sound collected by a sound collection device is obtained; A second acoustic signal is generated by rotating the phase of the first acoustic signal in one direction over time in parallel with the sound collection.

1. A computer-implemented method for audio processing, comprising: In generating the second acoustic signal, generating a third acoustic signal by varying a phase of the first acoustic signal; generating an intermediate signal having a predetermined phase difference with respect to the third acoustic signal by changing a phase of the first acoustic signal; generating the second acoustic signal by adding a fourth acoustic signal generated by multiplying the intermediate signal by a first weighting value and a fifth acoustic signal generated by multiplying the third acoustic signal by a second weighting value; The phase of the first acoustic signal is rotated by varying each of the first weighting value and the second weighting value over time. Acoustic processing methods.

3. Furthermore, the sound represented by the second sound signal is reproduced by a sound emitting device. The acoustic processing method according to claim 1 or 2.

4. The rotation speed of the phase is less than or equal to 2 revolutions per second. The acoustic processing method according to claim 1 or 2.

5. The rotation speed of the phase is equal to or greater than 0.01 revolutions per second. The acoustic processing method according to claim 1 or 2.

6. In generating the second acoustic signal, the phase of the first acoustic signal is rotated at a constant speed within an audible frequency band. The acoustic processing method according to claim 1 or 2.

7. The phase difference of the second acoustic signal relative to the first acoustic signal is equal within the audible frequency band. The acoustic processing method according to claim 6.

8. a signal acquisition unit that acquires a first acoustic signal representing a sound collected by a sound collection device; an audio processing unit that generates a second audio signal by rotating the phase of the first audio signal in one direction over time in parallel with the sound collection; Equipped with The acoustic processing unit includes: generating a third acoustic signal by varying a phase of the first acoustic signal; generating the second acoustic signal by adding a fourth acoustic signal generated by multiplying the first acoustic signal by a first weighting value and a fifth acoustic signal generated by multiplying the third acoustic signal by a second weighting value; The phase of the first acoustic signal is rotated by varying each of the first weighting value and the second weighting value over time. Sound processing system.

9. a signal acquisition unit that acquires a first acoustic signal representing a sound collected by a sound collection device; an audio processing unit that generates a second audio signal by rotating the phase of the first audio signal in one direction over time in parallel with the sound collection; Equipped with The acoustic processing unit includes: generating a third acoustic signal by varying a phase of the first acoustic signal; generating an intermediate signal having a predetermined phase difference with respect to the third acoustic signal by changing a phase of the first acoustic signal; generating the second acoustic signal by adding a fourth acoustic signal generated by multiplying the intermediate signal by a first weighting value and a fifth acoustic signal generated by multiplying the third acoustic signal by a second weighting value; The phase of the first acoustic signal is rotated by varying each of the first weighting value and the second weighting value over time. Sound processing system.

10. a signal acquisition unit that acquires a first acoustic signal representing a sound collected by a sound collection device; and an acoustic processing unit that generates a second acoustic signal by rotating the phase of the first acoustic signal in one direction over time in parallel with the sound collection; A program for causing a computer to function as The acoustic processing unit includes: generating a third acoustic signal by varying a phase of the first acoustic signal; generating the second acoustic signal by adding a fourth acoustic signal generated by multiplying the first acoustic signal by a first weighting value and a fifth acoustic signal generated by multiplying the third acoustic signal by a second weighting value; The phase of the first acoustic signal is rotated by varying each of the first weighting value and the second weighting value over time. program.

11. a signal acquisition unit that acquires a first acoustic signal representing a sound collected by a sound collection device; and an acoustic processing unit that generates a second acoustic signal by rotating the phase of the first acoustic signal in one direction over time in parallel with the sound collection; A program for causing a computer to function as The acoustic processing unit includes: generating a third acoustic signal by varying a phase of the first acoustic signal; generating an intermediate signal having a predetermined phase difference with respect to the third acoustic signal by changing a phase of the first acoustic signal; generating the second acoustic signal by adding a fourth acoustic signal generated by multiplying the intermediate signal by a first weighting value and a fifth acoustic signal generated by multiplying the third acoustic signal by a second weighting value; The phase of the first acoustic signal is rotated by varying each of the first weighting value and the second weighting value over time. program.

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