JP2010181448A - Sound adjusting device and sound adjusting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound adjusting device capable of accurately specifying acoustic characteristics of space by using a sound signal of colored notes, and to provide a sound adjusting method. <P>SOLUTION: The sound adjusting device for adjusting sound in a prescribed space comprises: a dividing means for dividing a sound source signal of colored notes which is reproduced by a loudspeaker, and a collected signal which is collected by a microphone, into a plurality of partial frequency bands; a determination means for determining whether or not the sound source signal is effective to estimate a transfer function on the basis of a signal level of a sound source signal in the partial frequency band; an estimation means for estimating the partial sound transfer function in the partial frequency band of the sound source signal and the collected signal on the basis of the sound source signal and the collected signal, which are determined to be effective by the determination means; and a synthesizing means for synthesizing the partial sound transfer functions estimated by the estimation means for a plurality of partial frequency bands. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an acoustic adjustment device and an acoustic adjustment method.

  Conventionally, an acoustic transfer function is estimated (identified) between a speaker and a listener who listens to music or the like emitted from the speaker in a predetermined space, and through an adaptive filter in which a filter coefficient is set based on the acoustic transfer function. A technique for improving the sense of reality of sound (for example, music) listened to by a listener by outputting an audio signal from a speaker is known.

  As a method for identifying an acoustic transfer function, a method using a predetermined signal generated for testing (hereinafter referred to as “white noise”) is generally used. When the acoustic transfer function is identified by this method, a microphone is installed at a position where the listener listens to music, and white noise emitted from the speaker is collected by the microphone.

  FIG. 1 is an explanatory view of a conventional acoustic transfer function identification method. As shown in FIG. 1A, white noise is a signal having a constant signal level from low frequency to high frequency. Therefore, this white noise is collected by a microphone, and the frequency characteristics and signal level of the signal obtained as a result are analyzed, so that a low frequency to a high frequency in the space between the speaker and the microphone is obtained as shown in FIG. The acoustic characteristics desired to be obtained can be calculated uniformly, and the acoustic transfer function can be identified based on the measurement results.

  As described above, white noise includes a wide frequency band from low frequency to high frequency, so it is an effective signal for use in identifying an acoustic transfer function. It is a sound. Therefore, the identification of the acoustic frequency due to white noise has been performed in advance when there is no listener or before music or the like is reproduced.

  As described above, when the acoustic transfer function is identified in advance, the space between the speaker and the listener is changed when the temperature or humidity of the space or the positional relationship between the speaker and the listener changes during reproduction of music or the like. There is a possibility that the acoustic characteristics in the case change. Therefore, it is desirable to identify the acoustic transfer function at any time, but since white noise is annoying sound for the listener as described above, identifying the acoustic transfer function by white noise during playback of music, etc. There may be a problem that the comfort of the listener is disturbed.

  As a technique for solving such a problem, a technique for identifying the acoustic characteristics of a space using a music signal output to a speaker during music playback instead of white noise has been devised (see, for example, Patent Document 1). ).

JP 2007-243242 A

  However, when a music signal is used as in the above prior art, the acoustic characteristics of the space may not be accurately measured, and the acoustic characteristics of the space may not be correctly identified.

  Since the music signal is a voice signal that changes the scale and the intensity of the sound as the melody progresses (hereinafter referred to as “colored sound”), the frequency ranges from low to high frequencies like white noise. In many cases, there is no constant signal level in the band.

  For example, as shown in FIG. 1C, a colored sound signal at a certain time (t) has a sufficiently high signal level in a relatively low frequency band (hereinafter referred to as “low frequency band”), Consider a case where the signal level in a relatively high frequency band (hereinafter referred to as “high frequency band”) is very low.

  In this case, if the actual acoustic characteristic in a certain space is the acoustic characteristic shown in FIG. 1B, the acoustic characteristic obtained by calculation is about the low frequency band as shown in FIG. Can reproduce sound characteristics satisfactorily because the signal level of the music signal is high enough, but in the high frequency range, the signal level of music signals is very low, so the sound characteristics can be reproduced well. This is not possible, and an acoustic characteristic having a signal level lower than that of the actual acoustic characteristic (the one-dot chain line in FIG. 1D) is reproduced.

  On the other hand, as shown in FIG. 1 (e), when a colored sound signal at a certain time (t + 1) has a very low signal level in the low frequency band and a sufficiently high signal level in the high frequency band. As shown in FIG. 1 (f), since the signal level of the music signal is sufficiently high in the high frequency band, the acoustic characteristics can be reproduced satisfactorily, but the signal level of the music signal is in the low frequency region. Is very low, the acoustic characteristics cannot be reproduced satisfactorily, and the acoustic characteristics having a signal level lower than the actual acoustic characteristics (the one-dot chain line in FIG. 1F) are reproduced.

  In this way, when the acoustic characteristics such as the acoustic transfer function of a certain space are identified using a colored sound signal, the frequency characteristics of the sound signal change over time, so the sound characteristics of the space can be measured accurately. In some cases, the acoustic characteristics of the space cannot be correctly identified.

  Accordingly, an object of the present invention is to provide an acoustic adjustment device and an acoustic adjustment method that can correctly identify the acoustic characteristics of a space using a colored sound signal.

  The present invention is an acoustic adjustment device that adjusts sound in a predetermined space by estimating an acoustic transfer function between a speaker and a microphone that collects sound reproduced by the speaker, and is reproduced by the speaker. A sound source signal of colored sound is divided into a plurality of partial frequency bands, and a sound collecting signal collected by the microphone is also divided into the partial frequency bands, and a signal level of the sound source signal in the partial frequency band is determined. Based on the sound source signal determined based on the sound source signal and the sound collection signal determined to be effective by the determination unit, the determination unit determining whether the sound source signal is effective in estimating the transfer function based on the sound source signal And an estimation means for estimating a partial acoustic transfer function representing the acoustic transfer function in the partial frequency band of the collected sound signal; It was decided to provide an acoustic adjustment apparatus and a combining means for combining said partial acoustic transfer function estimated by means for a plurality of said partial frequency bands.

  According to the present invention, based on a sound source signal determined to be valid and a sound collection signal in the same partial frequency band as the sound source signal, the sound source signal determined to be effective for estimating the transfer function in the partial frequency band In order to estimate the partial acoustic transfer function and synthesize the partial acoustic transfer functions estimated for each partial frequency band, when identifying acoustic characteristics such as acoustic transfer functions in a certain space using colored sound signals The acoustic characteristics of the space can be accurately measured, and the acoustic characteristics of the space can be correctly identified.

It is explanatory drawing of the identification method of the conventional acoustic transfer function. It is explanatory drawing which shows the example of application of the acoustic adjustment apparatus which concerns on this embodiment. It is a functional block diagram which shows the structure of the acoustic adjustment apparatus which concerns on this embodiment. It is explanatory drawing of the identification method of the acoustic transfer function by the acoustic adjustment apparatus which concerns on this embodiment. It is explanatory drawing which shows the procedure in which each partial acoustic transfer function is memorize | stored in a memory | storage part. It is explanatory drawing which shows the detailed structure of the acoustic adjustment apparatus which concerns on this embodiment. It is a flowchart which shows the flow of a process when CPU of DSP runs an acoustic adjustment program.

  Hereinafter, an embodiment of an acoustic adjustment device and an acoustic adjustment method according to the present invention will be specifically described with reference to the accompanying drawings. FIG. 2 is an explanatory diagram illustrating an application example of the acoustic adjustment device according to the present embodiment. As shown in FIG. 2, the acoustic adjustment device 10 according to the present embodiment includes music and voice stored in a portable storage medium such as a CD (Compact Disc) and a DVD (Digital Versatile Disc), a radio, a television, and a car navigation system. The audio or music signal (hereinafter referred to as “sound source signal”) input from the playback device 200 that outputs music or audio such as is output to the speaker 201 through the adaptive filter unit 62 (see FIG. 6) described later. Is a device that adjusts the sound in the space and improves the sense of reality of music or the like that the listener 203 listens to.

  Reference numeral 202 in FIG. 2 is a microphone that is installed near the listener 203 and collects colored sounds such as music output from the speaker 201. The microphone 202 converts the collected colored sound into a sound signal (hereinafter referred to as “sound collection signal”) and outputs the sound signal to the sound adjustment device 10. Here, the colored sound is a sound whose scale and intensity change with the progress of a melody or the like.

  In the acoustic adjustment device 10, the acoustic transfer function of the space between the speaker 201 and the listener 203 is estimated as needed based on the sound source signal input from the playback device 200 and the sound collection signal input from the microphone 202. . Then, the acoustic adjustment device 10 outputs a sound source signal to the speaker 201 through an adaptive filter in which a filter coefficient calculated based on the estimated acoustic transfer function is adjusted.

  Here, the structure of the acoustic adjustment apparatus 10 of this embodiment is demonstrated with reference to FIG. FIG. 3 is a functional block diagram showing the configuration of the acoustic adjustment device 10. As shown in FIG. 3, a dividing unit 20, a determining unit 30, an estimating unit 40, a storage unit 50, and a combining unit 60 are provided.

  The dividing unit 20 divides the colored sound source signal reproduced by the speaker 201 into a plurality of partial frequency bands, and the sound collection signal collected by the microphone 202 also has the same partial frequency as the partial frequency band of the sound source signal. It is a processing unit that functions as a dividing unit that divides the data into bands.

  In the present embodiment, the dividing unit 20 has a frequency band higher than the intermediate frequency (hereinafter referred to as “high frequency band”) with the intermediate frequency in the audible range (frequency range audible to humans) as the boundary for the sound source signal input from the playback device 200. H ”) and a frequency band equal to or lower than the intermediate frequency (hereinafter referred to as“ low frequency band L ”), and outputs the result to the determination unit 30.

  Similarly to the sound source signal, the dividing unit 20 has two partial frequencies, a high frequency band H whose frequency is higher than the intermediate frequency and a low frequency band L whose frequency is equal to or lower than the intermediate frequency. Divide into bands. The sound collection signal for each partial frequency band obtained by dividing the sound collection signal is output to the estimation unit 40.

  In the present embodiment, the sound source signal and the collected sound signal are each divided into two partial frequency bands by the dividing unit 20, but the number of partial frequency bands to be divided is not limited to this and is arbitrary. You may divide | segment into a partial frequency band. However, even when the sound source signal and the sound collection signal are divided into three or more partial frequency regions, the sound source signal and the sound collection signal are each divided by the same frequency width.

  The determination unit 30 is a processing unit that determines whether the sound source signal is effective for estimating the acoustic transfer function based on the signal level of each sound source signal in each partial frequency band input from the dividing unit 20. . The determination unit 30 determines that the sound source signal is effective for estimating the acoustic transfer function when each of the sound source signals in the high frequency band H and the low frequency band L is equal to or higher than a predetermined signal level. Output to 40.

  That is, the determination unit 30 includes a predetermined threshold as a reference for determining whether the sound source signal for each partial frequency band input from the dividing unit 20 is valid or invalid for estimation of the acoustic transfer function. As the threshold value set here, for example, the value of the signal level of white noise is used. And when the signal level of a sound source signal is more than this threshold value, it determines with the sound source signal being effective for estimation of an acoustic transfer function. Further, when the signal level of the sound source signal has not reached the predetermined signal level, the determination unit 30 discards the sound source signal without outputting it to the estimation unit 40.

  For example, when a sound source signal as shown in FIG. 4A is input to the dividing unit 20 at a certain time (t), the sound source signal shown in the region on the left side of the one-dot chain line shown in the center of FIG. Is input to the determination unit 30 as a sound source signal in the low frequency band L, and a sound source signal shown in a region on the right side of the dashed line shown in the center of FIG. The

  In this case, the determination unit 30 determines that the signal level of the sound source signal in the low frequency band L at the time (t) is equal to or higher than the threshold value, so that the sound source signal is effective for estimation of the sound transfer function. Output. On the other hand, the determination unit 30 determines that the signal level of the audio signal in the high frequency band H at time (t) is less than the threshold value, and discards the sound source signal without outputting it to the estimation unit 40 at the subsequent stage.

  Thereafter, when a sound source signal as shown in FIG. 4C is input to the dividing unit 20 at time (t + 1), the sound source shown in the region on the left side of the alternate long and short dash line shown in the center of FIG. The signal is input to the determination unit 30 as a sound source signal in the low frequency band L, and the sound source signal shown in the region on the right side of the dashed line shown in the center of FIG. 4C is input to the determination unit 30 as the sound source signal in the high frequency band H. Is done.

  In this case, the determination unit 30 determines that the signal level of the sound source signal in the low frequency band L at time (t + 1) is less than the threshold value, so that it is invalid, and does not output the sound source signal to the subsequent estimation unit 40. Discard. On the other hand, the determination unit 30 determines that the signal level of the sound source signal in the high frequency band H at the time (t + 1) is equal to or higher than the threshold value, so that it is effective for estimating the acoustic transfer function, and sends the sound source signal to the estimation unit 40 in the subsequent stage. Output.

  In the present embodiment, the determination unit 40 determines that the sound source signal having a signal level equal to or higher than the predetermined signal level is effective for estimating the acoustic transfer function. However, when the signal level of the sound source signal is within the predetermined range. The sound source signal may be determined to be effective for estimating the acoustic transfer function. With this configuration, when a sound source signal with an unnecessarily high signal level such as noise or illegal radio waves is input, the sound source signal is not determined to be effective for estimating the acoustic transfer function. It is possible to prevent a reduction in the estimation accuracy of the partial acoustic transfer function due to.

  Whether the sound source signal is effective for estimating the acoustic transfer function is based on an arbitrary value as long as the intensity of the sound source signal can be determined, such as the voltage value, current value, amplitude value, etc. of each sound source signal. Determination may be performed.

  The estimation unit 40 represents an acoustic transfer function in a partial frequency band of the sound source signal and the sound collection signal based on the sound source signal and the sound collection signal determined to be effective for estimating the sound transfer function by the determination unit 30. It is a process part which estimates a partial acoustic transfer function.

  The estimation unit 40 uses a known arithmetic expression for calculating an acoustic transfer function to calculate the speaker 201 based on the difference between a sound source signal having a signal level equal to or higher than a predetermined signal level and a sound collection signal in the same partial frequency band as the sound source signal. The acoustic characteristics in each partial frequency band in the space between the microphones 202 are calculated, the ideal partial acoustic transmission function is calculated from the acoustic characteristics, and the calculation result is output to the storage unit 50.

  For example, when the sound source signal as shown in FIG. 4A is input to the dividing unit 20 at time (t), the estimation unit 40 receives the sound source signal of the low frequency region L from the determination unit 30. As shown in FIG. 4B, only the acoustic characteristics related to the low frequency band L are calculated, and the partial acoustic transfer function related to the low frequency band L obtained from the acoustic characteristics is stored in the storage unit 50 in the subsequent stage.

  As described above, the sound source signal of the low frequency band L input to the determination unit 30 at this time is a signal having a signal level equal to or higher than a threshold value and a constant signal level similar to white noise. The unit 30 can calculate the acoustic characteristics of the space for the low frequency band L with the same reproducibility as when white noise is used.

  In addition, when a sound source signal as shown in FIG. 4C is input to the dividing unit 20 at time (t + 1), the estimation unit 40 receives only a sound source signal in the high frequency band H from the determination unit 30. Therefore, as shown in FIG. 4D, only the acoustic characteristics relating to the high frequency band H are calculated, and the partial acoustic transfer function relating to the high frequency band H obtained from the acoustic characteristics is stored in the storage unit 50 in the subsequent stage.

  At this time, the sound source signal in the high frequency band H input to the determination unit 30 is a signal having a signal level equal to or higher than the threshold value and a constant signal level similar to white noise. Regarding the band H, the acoustic characteristics of the space can be calculated with the same reproducibility as when white noise is used.

  The storage unit 50 stores a partial acoustic transfer function for each partial frequency band. The storage unit 50 corresponds to a memory in which a partial acoustic transfer function and a filter coefficient are set in later-described synthesis filter units 51 and 52 (see FIG. 6).

  Here, with reference to FIG. 5, a procedure for storing (setting) each partial acoustic transfer function in the storage unit 50 will be described. FIG. 5 is an explanatory diagram illustrating a procedure in which each partial acoustic transfer function is stored in the storage unit. 5A to 5E, the high frequency band H is indicated by H, the low frequency band L is indicated by L, the partial acoustic function is indicated by Y, the partial acoustic transfer function Y in the high frequency band H is indicated by YH, and the low frequency region L is indicated. The partial acoustic transfer function Y at is indicated by YL. The parentheses beside YH and YL indicate the time when the sound source signal is input to the acoustic adjustment device 10.

  In the state (time (0)) before the sound source signal is input to the acoustic adjustment device 10 of the present embodiment, the storage unit 50 has a standard high frequency band as an initial value as shown in FIG. And a partial acoustic transfer function YL (0) in a standard low frequency band are stored.

  Thereafter, it is assumed that a sound source signal is input to the acoustic adjustment device 10 at time (t). At this time, when it is determined that only the sound source signal in the high frequency band H is effective for estimating the acoustic transfer function with respect to the input sound source signal, the storage unit 50 stores the time (t) as shown in FIG. ), The partial acoustic transfer function YH (t) of the high frequency band H is stored. Here, since the sound source signal in the low frequency band L is determined to be invalid, the partial acoustic transfer function YL (0) of the low frequency band L stored as the initial value is held without being updated.

  Next, when it is determined at time (t + 1) that only the low frequency band L is effective for estimating the acoustic transfer function with respect to the sound source signal input to the acoustic adjustment device 10, the storage unit 50 stores FIG. As shown in (c), the partial acoustic transfer function Y in the low frequency band L is updated and stored as the partial acoustic transfer function YL (t + 1) in the low frequency region L at time (t + 1). Here, since the sound source signal in the high frequency band H is determined to be invalid, the partial acoustic transfer function YH (t) in the high frequency band H is held without being updated.

  Thereafter, when it is determined at time (t + 2) that only the high frequency band H is valid for the estimation of the acoustic transfer function with respect to the sound source signal input to the acoustic adjustment device 10, the storage unit 50 stores FIG. ), The partial acoustic transfer function YH (t + 1) in the high frequency band H is updated to YH (t + 2), and the partial acoustic transfer function YL (t + 1) in the low frequency band L is retained. .

  Then, at time (t + 3), when it is determined that only the low frequency band L is effective for estimating the acoustic transfer function with respect to the sound source signal input to the acoustic adjustment device 10, the partial sound in the high frequency band H is similarly applied. The transfer function YH (t + 2) is held, and the partial acoustic transfer function YL (t + 1) in the low frequency band L is updated to YL (t + 3).

  The synthesis unit 60 is a processing unit that synthesizes the partial acoustic transfer functions estimated by the estimation unit 40 for a plurality of partial frequency bands. The synthesizing unit 60 generates an acoustic transfer function corresponding to the acoustic characteristics of all frequency bands in the audible range by synthesizing the partial acoustic transfer functions for each partial frequency band stored in the storage unit 50.

  For example, the synthesizing unit 60 calculates acoustic characteristics as shown in FIGS. 4B and 4D by the estimating unit 40, and stores the partial acoustic transfer function obtained from these acoustic characteristics in the storage unit 50. 4E, by combining the partial acoustic transfer function of the low frequency band L and the partial acoustic transfer function of the high frequency band H stored in the storage unit 50 at that time, as shown in FIG. The acoustic characteristics of the space can be reproduced well for all frequency bands in the audible range.

  As described above, in the acoustic adjustment device 10 of the present embodiment, the colored sound source signal input from the playback device 200 is divided into a plurality of partial frequency bands, and the signal level of each divided sound source signal is equal to or higher than a predetermined signal level. When the sound source signal is determined to be, the partial sound transfer function in the partial frequency band of the sound source signal is estimated using the sound source signal.

  Therefore, in this acoustic adjustment device 10, each partial acoustic transfer function for each partial frequency band estimated by the estimation unit 40 uses a sound source signal having a constant signal level as in the case of using white noise. Therefore, the partial acoustic transfer function for each frequency band can be estimated, and by combining these partial acoustic transfer functions by the synthesizing unit 60, the acoustic characteristics of the space can be reproduced well for all frequency bands in the audible range. can do.

  In addition, in the acoustic adjustment device 10, the partial acoustic transfer function stored in the storage unit 50 is updated to the latest one every time the sound source signal is determined to be effective for estimating the acoustic transfer function during the input of the sound source signal. Therefore, for example, even when the acoustic characteristics of the space change during music playback, the partial acoustic transfer function is changed as needed according to the change in the acoustic characteristics, and ideally suited to changes in the environment. An acoustic transfer function can be obtained.

  Here, a more specific configuration of the acoustic adjustment device 10 according to the present embodiment and a signal flow in the acoustic adjustment device 10 will be described with reference to FIG. FIG. 6 is an explanatory diagram showing a detailed configuration of the acoustic adjustment device 10.

  As shown in FIG. 6, the acoustic adjustment device 10 includes a synchronization unit 71, a frequency conversion unit 81 for sound source signals, a frequency conversion unit 82 for sound collection signals, a high-pass filter unit 21 for sound source signals, a low-pass filter unit 22, 1/2 down-sampling units 91 and 92, high-pass filter unit 23 for collected signal, low-pass filter unit 24, 1/2 down-sampling units 93 and 94, level check units 31 and 32 for sound source signals, and adaptive control unit 41 , 42, 2 upsampling units 95 and 96, synthesis filter units 51 and 52, addition unit 61, adaptive filter unit 62, and inverse frequency conversion unit 100.

  The acoustic adjustment apparatus 10 is configured by a DSP (Digital Signal Processor) including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU of the DSP is stored in the ROM. By executing the stored predetermined sound adjustment program using the RAM as a work area, the synchronization unit 71, the frequency conversion unit 81, the frequency conversion unit 82, the high pass filter unit 21, the low pass filter unit 22, and 1/2 downsample Units 91 and 92, high-pass filter unit 23, low-pass filter unit 24, 1/2 down-sampling units 93 and 94, level check units 31 and 32, adaptive control units 41 and 42, up-sampling units 95 and 96, synthesis filter unit 51, 52, an adder 61, an adaptive filter 62, an inverse frequency converter 100, and the like.

  The synchronization unit 71 delays the sound source signal input from the playback device 200 to synchronize the phases of the sound source signal and the sound collection signal, and then outputs the sound source signal to the frequency conversion unit 81.

  The frequency conversion unit 81 for the sound source signal converts the sound source signal input from the synchronization unit 71 into a frequency domain by FFT (Fast Fourier Transform), and then outputs it to the high pass filter unit 21 and the low pass filter unit 22. At the same time, the sound source signal converted into the frequency domain is output to the adaptive filter 62.

  The frequency conversion unit 82 for the sound collection signal converts the sound collection signal input from the microphone 202 into the frequency domain by FFT, and then outputs it to the high pass filter unit 23 and the low pass filter unit 24.

  The high-pass filter unit 21 for the sound source signal cuts the low frequency band L component of the sound source signal converted into the frequency domain, generates a sound source signal having only the high frequency band H component, and outputs the sound source signal to the 1/2 down-sampling unit 91. . Further, the low-pass filter unit 22 for the sound source signal cuts the high frequency band H component of the sound source signal converted into the frequency domain, generates a sound source signal of only the low frequency band L, and outputs it to the 1/2 down-sampling unit 92 To do.

  Similarly, the high-pass filter unit 23 for the sound collection signal outputs a sound collection signal having only the high frequency band H component to the 1/2 down-sampling unit 93, and the low-pass filter unit 24 for the sound collection signal has a low frequency band L The collected sound signal of only the component is output to the 1/2 downsampling unit 94.

  The sound source signal 1/2 down-sampling units 91 and 92 sample (down-sample) each sound source signal input thereto at a sampling frequency that is 1/2 times the sound source signal frequency, and then each 1/2 down-sample. The data is output to the level check units 31 and 32 following the units 91 and 92.

  The sound collection signal 1/2 down-sampling units 93 and 94 sample (down-sample) the input sound collection signal at a sampling frequency that is 1/2 times the sound collection signal frequency, and then perform 1/2 down-sampling. The data is output to the adaptive control units 41 and 42 following the sample units 93 and 94.

  The level check units 31 and 32 determine whether or not the signal level of the sound source signal input to each is higher than or equal to a predetermined signal level, and each of the sound source signals determined to be higher than or equal to the predetermined signal level. The data is output to the adaptive control units 41 and 42 at the subsequent stage. On the other hand, when it is determined that the signal level has not reached the predetermined signal level, the level check units 31 and 32 discard the signal without outputting it to the adaptive control units 41 and 42.

  The adaptive control units 41 and 42 calculate the acoustic characteristics in the respective partial frequency bands based on the sound source signal and the collected sound signal respectively input thereto, and obtain partial acoustic transfer functions corresponding to the obtained acoustic characteristics. The identification processing is performed (estimated) by obtaining, and a signal to which the partial acoustic transfer function after the identification processing is applied is output to the 2-upsampling units 95 and 96 following the adaptive control units 41 and 42.

  The two up-sampling units 95 and 96 sample (up-sample) the input signals at a sampling frequency twice as high as the signal frequency, and then output the signals to the subsequent synthesis filter units 51 and 52.

  The synthesis filter units 51 and 52 are adaptive filters that self-adapt a partial acoustic transfer function in each partial frequency band in accordance with a known optimization algorithm. Self-adapt the filter coefficients applying the partial acoustic transfer function in the frequency band. Each of these synthesis filter units 51 and 52 updates the partial acoustic transfer function and filter coefficient based on the signal each time a signal is input from the two-upsampling units 95 and 96 in the previous stage.

  The adder 61 adds the high frequency band H synthesis filter 51 and the low frequency band L synthesis filter 52. By the addition processing of the adding unit 61, the filter coefficient in the subsequent adaptive filter unit 62 is determined. That is, as a result of this addition processing, the filter coefficient of the synthesis filter unit 51 is set as the filter coefficient in the high frequency band H of the adaptive filter unit 62, and the filter coefficient of the synthesis filter unit 52 is the filter in the low frequency band L of the adaptive filter unit 62. Set as a coefficient.

  The adaptive filter unit 62 subjects the sound source signal converted into the frequency domain input from the frequency conversion unit 81 to filter processing according to the filter coefficient set at that time, and outputs the result to the inverse frequency conversion unit 100. .

  The inverse frequency transform unit 100 converts the frequency domain sound source signal input from the adaptive filter unit 62 into the time domain by IFFT (Inverse Fast Fourier Transform), and then outputs the converted signal to the speaker 201.

  Next, processing executed by the CPU of the DSP when the acoustic adjustment device 10 performs acoustic adjustment will be described with reference to FIG. FIG. 7 is a flowchart showing the flow of processing when the CPU of the DSP executes the sound adjustment program.

  As shown in FIG. 7, the CPU first executes a synchronization process for synchronizing the phases of the sound source signal and the sound collection signal (step S101), and then converts the sound source signal and the sound collection signal into the frequency domain. Processing is executed (step S102).

  Subsequently, the CPU executes a dividing process of dividing the sound source signal and the collected sound signal converted into the frequency domain into the high frequency band H and the low frequency band L, respectively (step S103), and thereafter, 1 for each signal frequency. A downsampling process with a sampling frequency of / 2 is executed (step S104).

  Here, the CPU determines whether or not the signal level is equal to or higher than a predetermined signal level for each sound source signal of each partial frequency band subjected to the down-sampling process, so that the sound source signal is the acoustic transfer function. Processing for determining whether or not the estimation is effective is executed (step S105).

  Then, when the CPU determines that the sound source signal is effective for estimation of the acoustic transfer function (step S105: Yes), based on the sound source signal and the collected sound signal having the same partial frequency band, in the partial frequency band An identification process for estimating the partial sound transfer function is executed (step S106), and then an update process for updating the partial sound transfer function being set to the partial sound transfer function obtained by the current identification process is executed (step S107). ), And the process proceeds to step S108. On the other hand, if the CPU determines in step S105 that the sound source signal is not effective for estimating the acoustic transfer function (step S105: No), the process proceeds to step S108.

  Subsequently, the CPU executes an upsampling process (step 108), and then executes a synthesis process for synthesizing the synthesis filter unit 51 in the high frequency band H and the synthesis filter unit 52 in the low frequency band L (step S109). .

  Then, the CPU executes convolution processing by the adaptive filter unit 62 on the sound source signal (step S110), and then executes inverse frequency conversion processing for converting the sound source signal subjected to the convolution processing into the time domain. (Step S111), the post-processing output to the speaker 201 is terminated.

  As described above, in the acoustic adjustment device 10 according to the present embodiment, the sound source signal that is a colored sound input from the reproduction device 200 is used instead of white noise for identification of the acoustic transfer function. Even if the acoustic transfer function is identified, the comfort of the listener is not hindered.

  In addition, the sound adjustment device 10 converts the sound source signal input from the reproduction device 200 into a frequency domain and then divides the sound source signal into a plurality of partial frequency bands, and checks the signal level of the sound source signal for each partial frequency band. Thus, the partial acoustic transfer function in the partial frequency band is identified based on the sound source signal determined to have a signal level equal to or higher than the predetermined signal level and the sound collection signal in the same partial frequency band as the sound source signal. Even if the signal level input from the playback device 200 changes with time, the acoustic characteristics of the space are reproduced well in the partial frequency band where the signal level of the sound source signal is equal to or higher than the predetermined signal level. Therefore, the partial acoustic transfer function can be preferably identified.

  In the acoustic adjustment device 10, in the partial frequency band in which the signal level of the sound source signal divided for each partial frequency band is determined to be equal to or higher than the predetermined signal level, the synthesis filter unit corresponding to the partial frequency band In the partial frequency band in which the filter coefficients of 51 and 52 are updated and the signal level of the sound source signal is determined to be less than the predetermined signal level, the filter coefficients of the synthesis filter units 51 and 52 corresponding to the partial frequency band are changed. The filter coefficient updated last time is held without updating.

  Therefore, in this acoustic adjustment device 10, when a sound source signal that is not suitable for identification of a partial acoustic transfer function, such as a sound source signal with a very low signal level, is input, the synthesis filter units 51, 52 are based on the sound source signal. Since the filter coefficient is not updated, it is possible to prevent the reproducibility of the acoustic characteristics from being reduced.

  Further, in the above-described embodiment, the partial acoustic transfer function in the standard high frequency band as the initial value and the standard low frequency band are stored in the storage unit 50 before the sound source signal is input to the acoustic adjustment device 10. Are stored, but when the input of the sound source signal is stopped, the storage unit 50 inputs the sound source signal next to each of the partial sound transfer functions stored at that time. Hold up.

  Thereby, when this acoustic adjustment device 10 is applied to an in-vehicle audio system or the like, even if the engine is stopped during music playback, the engine is stopped in the storage unit 50 when the engine is restarted. Since each partial acoustic transfer function is held, the time required to identify the acoustic transfer function can be shortened.

DESCRIPTION OF SYMBOLS 10 Acoustic adjustment apparatus 20 Dividing part 30 Determination part 40 Estimation part 50 Storage part 60 Synthesis | combination part 200 Playback apparatus 201 Speaker 202 Microphone 203 Listener

Claims (3)

An acoustic adjustment device that adjusts sound in a predetermined space by estimating an acoustic transfer function between a speaker and a microphone that collects sound reproduced by the speaker,
A dividing unit that divides a colored sound source signal reproduced by the speaker into a plurality of partial frequency bands, and also divides a collected signal collected by the microphone into the partial frequency band;
Determining means for determining whether the sound source signal is effective for estimating a transfer function based on a signal level of the sound source signal in the partial frequency band;
Estimation that estimates a partial sound transfer function representing the sound transfer function in the partial frequency band of the sound source signal and the sound collection signal based on the sound source signal and the sound collection signal determined to be effective by the determination unit Means,
Synthesizing means for synthesizing the partial acoustic transfer functions estimated by the estimating means for a plurality of the partial frequency bands;
An acoustic adjustment device comprising: Storage means for storing the partial acoustic transfer function for each partial frequency band;
The estimation means causes the storage means to store the partial acoustic transfer function estimated based on the sound source signal and the sound collection signal determined to be effective for estimation of a transfer function by the determination means,
2. The acoustic adjustment apparatus according to claim 1, wherein the synthesizing unit synthesizes the partial acoustic transfer function for each partial frequency band stored in the storage unit. An acoustic adjustment method by an acoustic adjustment device that adjusts sound in a predetermined space by estimating an acoustic transfer function between a speaker and a microphone that collects sound reproduced by the speaker,
The acoustic adjustment device is
A division step of dividing the colored sound source signal reproduced by the speaker into a plurality of partial frequency bands, and also dividing the collected sound signal collected by the microphone into the partial frequency band;
A determination step of determining whether the sound source signal is effective for estimating a transfer function based on the signal level of the sound source signal in the partial frequency band;
A partial acoustic transfer function representing the acoustic transfer function in the partial frequency band of the sound source signal determined to be effective based on the sound source signal determined to be effective and the sound collection signal determined by the determination step; An estimation step to estimate;
And a synthesis step of synthesizing the partial acoustic transfer functions estimated in the estimation step for a plurality of the partial frequency bands.

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