JP2007331557A - Acoustic system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acoustic system which highly accurately and efficiently reduces noise of frequencies in from low to medium-high bands. <P>SOLUTION: The acoustic system 1 is provided with: a reference microphone 7 receiving sound to become sound attenuation object; an L microphone 5L and a R microphone 5R provided near the left/right ears of a user; a medium-high frequency band first sound correction means 9 reducing the medium-high band noise near the left ear position, based on an acoustic signal received by the reference microphone 7 and an acoustic signal received by the L microphone 5L; a medium-high band second sound correction means 10 reducing the medium-high band noise near the right ear position, based on the acoustic signal received by the reference microphone 7 and an acoustic signal received by the R microphone 5R; and a low band sound correction means 11 reducing the low band noise near the right/left ears positions of the user, based on the acoustic signal received by the reference microphone 7 and the acoustic signals received by the L microphone 5L and the R microphone R. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an acoustic system capable of reducing noise from a low range to a mid-high range in a vehicle interior or the like.

  Conventionally, active noise control (ANC) is known as one of the techniques for reducing ambient noise. This is a technique for canceling noise by receiving noise with a microphone and outputting a sound of opposite phase from a speaker.

In order to reduce noise in the vehicle, various configurations have been proposed in the past, and as an example, a method of performing ANC control using a speaker installed in a vehicle door has been proposed (Patent Document 1). reference).
Japanese Patent Laid-Open No. 11-133981

  However, in the speaker installed on the vehicle door, the sound deadening position, specifically, the vicinity of the ear position of the user who gets on the vehicle and the installation position of the speaker are relatively far away, so that the propagation loss is large and the speaker output is large. There was a problem that the output level was required.

  In addition, in the middle and high frequency range with a short wavelength, there is a problem that the acoustic characteristics are easily changed by a person or a load, and the applicable frequency is limited to the low range.

  In addition, when the door is opened and closed, the distance from the user's ear position to the speaker changes, so the sound propagation distance to the mute position changes, the acoustic characteristics change significantly, and the noise reduction effect is reduced. was there.

  This invention is made | formed in view of the said problem, and makes it a subject to provide the acoustic system which can reduce the noise of the frequency from a low region to a mid-high region highly accurately and efficiently.

  In order to solve the above problems, an acoustic system according to the present invention includes a reference microphone that receives a sound to be muffled, an L microphone provided in the vicinity of the user's left ear position, and a position near the user's right ear position. In the vicinity of the left ear position of the user based on the R microphone provided, the mid-high range acoustic signal of the sound received by the reference microphone, and the mid-high range acoustic signal of the sound received by the L microphone Middle / high range first acoustic correction means for generating a first acoustic signal for reducing middle / high range noise, middle / high range acoustic signal received by the reference microphone, and sound received by the R microphone Received by the reference microphone, and second and second mid-high range acoustic correction means for generating a second acoustic signal for reducing mid-high range noise in the vicinity of the right ear position of the user based on the middle and high range acoustic signal Sound Third sound for reducing low-frequency noise in the vicinity of the left and right ear positions of the user based on a low-frequency acoustic signal and a low-frequency acoustic signal received by the L microphone and the R microphone. Low-frequency sound correcting means for generating a signal, an L speaker for outputting an output sound composed of the first sound signal and the third sound signal in the vicinity of the left ear position of the user, the second sound signal, and the And an R speaker that outputs an output sound including the third acoustic signal in the vicinity of the right ear position of the user.

  The L speaker and the R speaker are preferably full-range speakers capable of outputting an output sound from a low frequency to a high frequency.

  Further, in this acoustic system, the L microphone and the L speaker are disposed in the upper left part of the vehicle seat, and the R microphone and the R speaker are disposed in the upper right part of the vehicle seat. Also good.

  According to the acoustic system of the present invention, the sound range to be muffled is frequency-divided into the low range and the mid-high range, and noise is reduced in the high range by the mid-high range first acoustic correction means and the mid-high range second acoustic correction means. Since the processing can be performed and the noise reduction processing in the low frequency can be performed by the low frequency acoustic correction means, it is possible to effectively perform the silencing processing.

  Furthermore, in the mid-high range silencing process, the silencing area is divided into a right part and a left part according to the user's ear position, and noise reduction processing is performed independently, so noise processing can be performed with higher accuracy. Thus, a more effective silencing effect can be obtained.

  In addition, the number of speakers can be reduced to two by using full-range speakers capable of outputting low-frequency to high-frequency output sounds as the L and R speakers, and the system configuration can be simplified. .

  Furthermore, by arranging the L microphone and the L speaker in the upper left part of the vehicle seat and arranging the R microphone and the R speaker in the upper right part of the vehicle seat, the user can more effectively enjoy the silencing effect. Is possible.

  The acoustic system according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of the acoustic system 1. The acoustic system 1 is installed in the interior of a vehicle and, as shown in FIG. 1, a muffler speaker installed on the left and right (left and right facing the front direction) of the headrest portion 3 of the vehicle seat (vehicle seat) 2. 4L (L speaker), 4R (R speaker), error microphones 5L (L microphone), 5R (R microphone) installed in the vicinity of the mute speakers 4L, 4R, the apparatus main body 6 that performs noise control, and the mute It has a reference microphone 7 that receives target noise (noise / noise).

  As the mute speakers 4L and 4R, full-range speakers capable of outputting sounds from low to high frequencies are used, and the headrests are arranged in the vicinity of the left and right ear positions of the user seated on the seat 2. It is provided in the part 3. The output surfaces of the muffler speakers 4L and 4R are arranged in a forward direction of the seat 2 and tilted inward by a predetermined angle toward the user's ear position direction.

  In addition, the error microphones 5L and 5R are also installed in the headrest portion 3, and the right and left ears of the user seated on the seat 2 are acquired in order to obtain the correction data (correction sound) for the silencing process in the vicinity of the user's left and right ear positions. It is provided near the position. For this reason, the mute speakers 4L and 4R and the error microphones 5L and 5R are arranged at positions close to each other.

  Note that the mute speakers 4L and 4R and the error microphones 5L and 5R are not necessarily installed in the headrest portion 3, and may be disposed in the vicinity of the left and right ear positions of the user. It may be a thing.

  The reference microphone 7 is installed, for example, in an engine room or a trunk room in order to receive noise to be silenced. For example, when the acoustic system according to the present embodiment is installed for the purpose of silencing the engine driving sound, the reference microphone 7 is disposed in the engine room, and the engine driving sound is received by the reference microphone 7. . In the present embodiment, only one reference microphone 7 is described, but a plurality of reference microphones 7 may be provided according to the noise target.

  As shown in FIG. 2, the apparatus main body 6 includes a mid-high range ANC unit L (first mid-high range acoustic correction unit) 9, a mid-high range ANC unit R (second mid-high range second acoustic correction unit) 10, and The ANC unit for low frequency (sound correction means for low frequency) 11 is provided. Furthermore, the apparatus main body 6 includes three HPFs (high-pass filters) 12a to 12c that allow only the mid-high range signal among the signals input to the mid-high range ANC unit L9 and the mid-high range ANC unit R10, Two LPFs (low-pass filters) 13 a and 13 b that pass only low-frequency signals among signals input to the low-frequency ANC unit 11 are provided. In this embodiment, the HPFs 12a to 12c and the LPFs 13a and 13b allow input signals to be input into a sound range of 250 Hz or more (this sound range is a medium to high frequency) and a sound range of 250 Hz or less (this sound range is a low frequency). Shall be divided.

  FIG. 3 is a block diagram showing a schematic configuration of the low-frequency ANC unit 11.

  The low-frequency ANC unit 11 cancels the low-frequency output sound that cancels (silences) the surrounding sound collected by the reference microphone 7 based on the acoustic signals collected by the error microphone 5L and the error microphone 5R. An acoustic signal to be output from the speakers 4L and 4R is created. As an ANC processing algorithm, a known algorithm such as Filtered-x LMS (LMS: least mean square) or Filtered-reference LMS can be used.

  As shown in FIG. 3, the low-frequency ANC unit 11 includes a delay unit 15, an acoustic correction unit 16, an LMS unit 17, an FIR filter unit 18, and a multiplication unit 19.

  The delay unit 15 performs delay processing of the sound signal received by the reference microphone 7 in consideration of the delay time from the mute speakers 4L, 4R to the error microphones 5L, 5R, the response time of the mute speakers 4L, 4R, and the like. It is provided for.

  The acoustic correction unit 16 is provided for correcting acoustic characteristics from the mute speakers 4L and 4R to the error microphones 5L and 5R. As shown in FIG. 4 (a), the output sound of the mute speaker 4L provided on the left side of the headrest portion 3 of the seat is the error installed on the right side as well as the error microphone 5L installed on the left side of the user U. It is also transmitted to the microphone 5R. At this time, the sound pressure level of the output sound from the mute speaker 4L to the error microphones 5L, 5R changes according to the frequency while passing through the space.

  For example, as shown in FIG. 4A, when a low frequency sound is output from the mute speaker 4L and the mute speaker 4R, the sound of the mute speaker 4L is transmitted to the error microphone 5L installed on the left side of the user U. The frequency characteristic when the sound is transmitted to the error microphone 5L installed on the left side of the user U is C12a, and the sound of the mute speaker 4L is installed on the right side of the user U. If the frequency characteristic when C21a is transmitted to the error microphone 5R and the frequency characteristic when the sound of the mute speaker 4R is transmitted to the error microphone 5R installed on the right side of the user U is C22a, the mute speaker 4L and The acoustic characteristics of the low frequency sound in the muffler speaker 4R are shown as in FIG. The acoustic correction unit 16 performs acoustic correction processing on a low-frequency acoustic signal (acoustic signal of the reference microphone 7 subjected to delay processing by the delay unit 15) based on the acoustic characteristics shown in 4 (b).

  Based on the acoustic signal received from the error microphones 5L and 5R and the acoustic signal of the reference microphone 7 that has been acoustically corrected by the delay unit 15 and the acoustic correction unit 16, the LMS unit 17 uses the least squares algorithm to generate an FIR filter unit. 18 coefficient control is performed.

  The FIR filter is a finite impulse response filter, and the acoustic signal received by the reference microphone 7 is processed based on the FIR filter unit 18 whose coefficient is controlled by the LMS unit 17. The output signal processed by the FIR filter unit 18 is inverted in phase by the multiplication unit 19 and output from the mute speaker 4L and the mute speaker 4R.

  The mid-high range ANC unit L9 cancels (silences) the surrounding sounds collected by the reference microphone 7 based on the acoustic signal collected by the error microphone 5L, and the mute speakers 4L, 4R. Create an acoustic signal to be output from. Further, the mid-high range ANC unit R10 cancels (mutes) the surrounding sound collected by the reference microphone 7 based on the acoustic signal collected by the error microphone 5R, and outputs the mid-high range output sound as the mute speaker 4L. An acoustic signal to be output from 4R is created.

  The configurations of the mid-high range ANC unit L9 and the mid-high range ANC unit R10 are the same as the configurations of the low-range ANC unit 11 shown in FIG. In addition, the ANC unit R10 for middle and high frequencies is different from the ANC unit 11 for low frequencies in application coefficients such as the filter length of the FIR filter unit and the step size and leak factor of the LMS unit.

  In addition, since the acoustic correction units for the mid-high range ANC unit L9 and the mid-high range ANC unit R10 are also corrected in accordance with the high-frequency range acoustic signal, the acoustic characteristics used during correction are low-frequency acoustic signals. It is different from the case of.

  As shown in FIG. 5A, when the middle and high range sound is output from the mute speaker 4L and the mute speaker 4R, the sound of the mute speaker 4L is transmitted to the error microphone 5L installed on the left side of the user U. The frequency characteristic is C11b, the frequency characteristic when the sound of the mute speaker 4R is transmitted to the error microphone 5L installed on the left side of the user U is C12b, and the sound of the mute speaker 4L is installed on the right side of the user U When the frequency characteristic when being transmitted to 5R is C21b, and the frequency characteristic when the sound of the mute speaker 4R is transmitted to the error microphone 5R installed on the right side of the user U is C22b, the medium and high sound in the mute speaker 4L The acoustic characteristics of the area are shown as in FIG. 5B, and the acoustic characteristics of the mid-high range in the mute speaker 4R are shown as in FIG. 5C.

  In FIG. 5B, the level of the acoustic characteristic C11b of the sound transmitted from the mute speaker 4L to the error microphone 5L installed on the left side of the user U is set on the right side of the user U from the mute speaker 4L. The value is higher than the level of the acoustic characteristic C21b of the sound transmitted to the error microphone 5R. This is because the sound output from the mute speaker 4L is blocked by the user U's own head, and further, since the output sound is in a high frequency range, it is difficult to be transmitted to the error microphone 5R installed on the right side of the user U. For this reason, the acoustic correction unit of the mid-high range ANC unit L9 performs the acoustic correction process on the acoustic signal using only the acoustic characteristic C11b. Similarly, the acoustic correction unit of the mid-high range ANC unit R10 performs the acoustic correction process on the acoustic signal using only the acoustic characteristic C22b having a high level in FIG. In this way, in the mid-high range acoustic correction process, the level of the acoustic characteristic (cross component) at which the muffler speaker and the error microphone cross each other is low, so that the acoustic correction unit 16 can be set without considering the cross component. It is possible to perform a mute control process spatially independent on the left and right.

  As shown in FIG. 2, the low-frequency ANC unit 11 synthesizes the sounds received by the error microphone 5L and the error microphone 5R by the adder 21a and performs an ANC process to obtain a mid-high frequency ANC unit L9. The ANC processing is performed using only the error microphone L and only the error microphone R in the middle / high frequency band ANC unit R10. This is because the acoustic signal to be subjected to ANC processing in the low-frequency ANC unit 11 has a characteristic that the frequency is 250 Hz or less and the wavelength becomes long, and the installation positions of the error microphone 5L and the error microphone 5R. This is because it is possible to determine that it is not necessary to divide and perform the ANC processing in consideration of the interval.

  On the other hand, the acoustic signal to be subjected to ANC processing in the mid-high range ANC unit L9 and the mid-high range ANC unit R10 has a feature that the frequency is 250 Hz or more and the wavelength is short. This is because it can be determined that it is preferable to divide and perform the ANC process in consideration of the interval between the installation positions with 5R. Similarly, the sound signal that has been ANC processed by the low-frequency ANC unit 11 is distributed and output to the mute speaker 4L and the muffler speaker 4R, respectively, but the sound that has been ANC-processed by the mid-high frequency ANC unit L9. The signal is output only to the silencer speaker 4L, and the acoustic signal that has been subjected to the ANC process in the ANC unit R10 for middle and high frequencies is output only to the silencer speaker 4R.

  When the muffling process is performed using the acoustic system configured as described above, only the mid-high range noise (signal) is received from the mid-high range ANC unit L9 and the mid-high level among the noise received by the reference microphone 7 by the HPF 12a. The signal is input to the area ANC unit R10. On the other hand, the sound in the vicinity of the left ear position of the user U received by the error microphone 5L is extracted by the HPF 12b only in the middle / high range and input to the middle / high range ANC unit L9, and the user listened to by the error microphone 5R. For the sound near the right ear position, only the mid-high range is extracted by the HPF 12c and input to the mid-high range ANC unit R10. In the mid-high range ANC unit L9, after the noise received by the reference microphone 7 is processed by the FIR filter unit in which coefficient control is performed based on the sound received by the error microphone 5L, the phase is changed. The inverted output signal La for muting (first acoustic signal) is generated. Similarly, in the mid-high range ANC unit R10, after the noise received by the reference microphone 7 is processed by the FIR filter unit in which coefficient control is performed based on the sound received by the error microphone 5R. Then, the output signal Ra (second acoustic signal) for muting whose phase is inverted is generated.

  FIG. 6A shows the frequency characteristics in the vicinity of the error microphone 5L when no muffling processing is performed. FIG. 6B shows that the mid-high frequency range is silenced only by the mid-high frequency ANC section L9. The frequency characteristics are shown. As is clear from the comparison between FIG. 6A and FIG. 6B, in FIG. 6B, the noise can be reduced by about 8 db in the mid-high range. Even when the frequency characteristics near the error microphone 5R are compared, the same silencing effect can be achieved.

  On the other hand, of the noise received by the reference microphone 7, only the low-frequency noise is input to the low-frequency ANC unit 11 by the LPF 13 a, and the synthesized signal received by the error microphone 5 L and the error microphone 5 R is , Only the low sound range is extracted by the LPF 13 b and input to the low frequency ANC unit 11. In the low-frequency ANC unit 11, the noise received by the reference microphone 7 is processed by the FIR filter unit 18 in which coefficient control is performed based on the sound received by the error microphone 5L and the error microphone 5R. After that, a silencing output signal LR (third acoustic signal) whose phase is inverted is generated.

  FIG. 7A shows the frequency characteristics in the vicinity of the error microphone 5L when no muffling processing is performed. FIG. 7B shows that the low frequency ANC section 11 performs muffing processing only on the low frequency range. The frequency characteristics are shown. As is clear from the comparison between FIG. 7A and FIG. 7B, in FIG. 7B, the noise can be reduced by about 10 db in the low band.

  The output signal La that has been silenced by the ANC section L9 for middle and high frequencies and the output signal LR that has been silenced by the ANC section 11 for low frequencies are added together by the adder 21b and output from the silencer speaker 4L.

  FIG. 8A shows the frequency characteristics in the vicinity of the error microphone 5L when no silencing processing is performed. FIG. 8B shows the output signal La and the output signal LR added by the adder 21b. The frequency characteristic of the output signal which consists of is shown. As is clear from the comparison between FIG. 8A and FIG. 8B, in FIG. 8B, noise can be reduced by about 8 db in the middle and high ranges and by about 10 db in the low ranges. It was.

  Further, the output signal Lb that has been silenced by the ANC section R10 for middle and high frequencies and the output signal LR that has been silenced by the ANC section 11 for low frequencies are added together by the adder 21c and output from the silencer speaker 4R. Even in the vicinity of the error microphone 5R, the noise can be reduced by about 8 db in the middle and high range and about 10 db in the low range.

  As described above, by using the sound system according to the present invention, the sound range to be muffled is frequency-divided into the low range and the mid-high range, and the ANC process in the low range and the ANC process in the mid-high range are separately performed. Thus, it is possible to effectively perform a silencing process.

  Furthermore, in the mid-high range, the noise reduction area is divided into a right part and a left part according to the position of the user's ear, and the ANC process is performed independently to reduce noise more accurately. Is possible.

  In addition, by using a full range speaker that can reproduce from low to high frequencies as a muffler speaker, the number of speakers can be reduced to simplify the configuration, and the vicinity of the user's ear position such as the headrest portion 3 of the seat In addition, by installing the mute speakers 4L and 4R and the error microphones 5L and 5R, the user can enjoy the mute effect more effectively.

  The acoustic system according to the present invention has been described above with reference to the drawings. However, the acoustic system according to the present invention is not limited to the above-described embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

It is the figure which showed schematic structure of the acoustic system which concerns on embodiment. 1 is a block diagram illustrating a schematic configuration of an acoustic system according to an embodiment. It is the block diagram which showed schematic structure of the ANC part for low frequencies which concerns on embodiment. (A) is the figure which showed the positional relationship of the mute speaker 4L, 4R, the error microphone 5L, 5R, and a user, (b) is the graph which showed the acoustic characteristic in the low frequency output sound. (A) is the figure which showed the positional relationship between the muffler speakers 4L and 4R, the error microphones 5L and 5R, and the user, and (b) is a graph showing the acoustic characteristics of the output sound in the mid-high range (mute speaker 4L). Yes, (c) is a graph showing the acoustic characteristics of the output sound of the mid-high range (silencer speaker 4R). (A) is the graph which showed the frequency characteristic of the error microphone 5L vicinity position when the muffling process is not carried out at all, (b) is muffled only in the mid-high range by the mid-high range ANC part L9. It is the graph which showed the frequency characteristic in the case. (A) is the graph which showed the frequency characteristic of the error microphone 5L vicinity position when the muffling process is not performed at all, and (b) is the case where the muffle process is applied only to the low frequency range by the low frequency ANC unit 11 It is the graph which showed the frequency characteristic. (A) is a graph showing the frequency characteristics of noise in the vicinity of the error microphone 5L when no muffling processing is performed, and (b) is muffled by the ANC unit L9 for middle and high frequencies and the ANC unit 11 for low frequencies. It is the graph which showed the frequency characteristic at the time of processing.

Explanation of symbols

1 ... Acoustic system 2 ... Seat (vehicle seat)
3 ... headrest part 4L, 4R ... mute speaker (L speaker, R speaker)
5L, 5R ... Error microphone (L microphone, R microphone)
6 ... Device main body part 7 ... Reference microphone 8 ... Backrest part 9 ... ANC part L for middle and high frequencies (first acoustic correction means for middle and high frequencies)
10: ANC part R for middle and high range (second acoustic correction means for middle and high range)
11 ... ANC section for low frequencies (acoustic correction means for low frequencies)
12a to 12c ... high-pass filters 13a and 13b ... low-pass filter 15 ... delay unit 16 ... acoustic correction unit 17 ... LMS unit 18 ... FIR filter unit 19 ... multiplication units 21a, 21b, and 21c ... adder U ... user

Claims (3)

A reference microphone that receives the sound to be muted,
An L microphone provided near the user's left ear position;
An R microphone provided near the right ear position of the user;
Based on the mid-high range acoustic signal of the sound received by the reference microphone and the mid-high range acoustic signal of the sound received by the L microphone, the mid-high range noise near the left ear position of the user is reduced. First acoustic correction means for middle and high ranges for generating a first acoustic signal for
Based on the mid-high range acoustic signal of the sound received by the reference microphone and the mid-high range acoustic signal of the sound received by the R microphone, the mid-high range noise near the right ear position of the user is reduced. Second acoustic correction means for middle and high ranges for generating a second acoustic signal for
Based on the low frequency sound signal of the sound received by the reference microphone and the low frequency sound signal of the sound received by the L microphone and the R microphone, the low frequency near the left and right ear positions of the user is determined. Low-frequency acoustic correction means for generating a third acoustic signal for reducing regional noise;
An L speaker that outputs an output sound composed of the first acoustic signal and the third acoustic signal in the vicinity of the left ear position of the user;
An R speaker that outputs an output sound composed of the second acoustic signal and the third acoustic signal in the vicinity of the right ear position of the user;
An acoustic system comprising:   The acoustic system according to claim 1, wherein the L speaker and the R speaker are full-range speakers capable of outputting an output sound from a low range to a high range. The L microphone and the L speaker are disposed at an upper left portion of a vehicle seat, and the R microphone and the R speaker are disposed at an upper right portion of the vehicle seat. The acoustic system according to 2.

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