JP2008205804A - Acoustic system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acoustic system capable of highly accurately and efficiently reducing noise in frequencies from a low band up to a medium-high band. <P>SOLUTION: The acoustic system 1 includes a reference microphone noise correction means 13 capable of smoothing frequency characteristics by applying filter processing to a sound to be muted which is collected by a reference microphone 7, and correction microphone noise correction means 14, 15 capable of smoothing the frequency characteristics by applying filter processing to sounds collected by correction microphones 5L, 5R arranged in the vicinity of user's ear positions. Further, the acoustic system 1 includes acoustic correction means 11, 12 for generating acoustic signals for reducing noise in the vicinity of the user's ear positions on the basis of sound filtered by the reference microphone noise correction means 13 and sound filtered by the correction microphone correction means 14, 15, and speakers 4L, 4R for outputting the acoustic signals. <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.

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

In order to reduce noise in the vehicle, various configurations have been proposed, and as an example, a method of performing ANC control using a speaker installed in a vehicle door has been proposed (for example, Patent Documents). 1).
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 or closed when the vehicle is stopped, the distance from the user's ear position to the speaker changes, so the sound propagation distance to the mute position changes, and the acoustic characteristics change greatly. There was a problem that the effect would be reduced.

  In addition, when the vehicle is traveling, the magnitude and characteristics of the noise that enters the passenger compartment change according to the traveling speed of the vehicle. Therefore, only the mute control using active noise control causes a processing delay as the processing load increases. Etc. may occur.

  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 collects a sound to be silenced, a correction microphone that is provided near the user's ear position, and a reference that is collected by the reference microphone. Filtering is applied to the reference microphone noise correcting means for applying a filter process to the microphone sound signal to flatten the frequency characteristics of the reference microphone sound, and a correction microphone sound signal being picked up by the correction microphone is filtered. The correction microphone noise correction means for flattening the frequency characteristics of the correction microphone sound, the reference microphone sound signal filtered by the reference microphone noise correction means, and the correction microphone noise correction means An acoustic signal for reducing noise in the vicinity of the user's ear position based on the corrected microphone sound signal subjected to the processing; And acoustic correction means for forming, characterized in that it comprises a speaker for outputting the output sound of the acoustic signal generated by the acoustic correcting means in the vicinity of the ear position the user.

  In the above acoustic system, since the noise correction process is performed by the acoustic correction unit after the frequency characteristic of the reference microphone sound (for example, noise) is flattened by the reference microphone noise correction unit, the reference microphone sound is reduced with a constant response time. It is possible to mute uniformly over the entire band from high to high.

  Furthermore, since the sound correcting means performs the mute processing of the reference microphone sound using the corrected microphone sound whose frequency characteristics are flattened by the correcting microphone noise correcting means, the sound correcting means can effectively perform the muffling processing by the sound correcting means. It is possible to mute the reference microphone sound throughout the entire band from low to high.

  In the acoustic system, the correction microphone includes an L microphone provided in the vicinity of the user's left ear position and an R microphone provided in the vicinity of the user's right ear position, and the correction microphone noise correction unit. Is applied to the acoustic signal of the corrected microphone sound collected by the L microphone, and the noise correction means for the L microphone for flattening the frequency characteristics of the corrected microphone sound and the sound collected by the R microphone. R microphone noise correcting means for applying a filtering process to the corrected microphone sound signal to flatten the frequency characteristics of the corrected microphone sound, and the acoustic correcting means filters the reference microphone noise correcting means. Based on the processed reference microphone sound signal and the corrected microphone sound signal filtered by the L microphone correction means L channel acoustic correction means for generating an L channel acoustic signal for reducing noise in the vicinity of the user's left ear position, and a reference microphone sound acoustic signal filtered by the reference microphone noise correction means And an R-channel acoustic signal for generating an R-channel acoustic signal for reducing noise in the vicinity of the right ear position of the user, based on the acoustic signal of the corrected microphone sound that has been filtered by the R microphone correcting means. Sound correction means, and the speaker outputs an output sound of the L channel acoustic signal in the vicinity of the left ear position of the user, and outputs an output sound of the R channel acoustic signal to the right of the user. And an R speaker that outputs in the vicinity of the ear position.

  In such an acoustic system, in order to mute the reference microphone, an L microphone and an R microphone are installed near the left and right ear positions of the user, respectively, and corrected microphone sounds collected from the L microphone and the R microphone, respectively. (Error sound) is flattened using the L microphone noise correcting means and the R microphone noise correcting means, and further, the reference microphone picked up by the reference microphone using the flattened left and right corrected microphone sounds. The sound (noise) is muffled separately on the left and right using the L channel sound correction means and the R channel sound correction means, so that the space is divided into left and right, and independent mute control is performed in the vicinity of the user's left and right ears. be able to. For this reason, even when there is a difference in the noise at the left and right ear positions, it is possible to reduce the noise from the low range to the mid-high range with high accuracy and efficiency in accordance with each noise.

  Further, in the acoustic system, the L microphone and the L speaker are disposed at an upper left portion of a seat on which the user is seated, and the R microphone and the R speaker are disposed at an upper right portion of the seat. May be.

  Thus, by arranging the L microphone and the L speaker at the upper left part of the seat and the R microphone and the R speaker at the upper right part of the seat, the ear position of the user sitting on the seat, the left and right microphones, and the left and right speakers are arranged. Since the position is always kept constant, the user can enjoy a stable silencing effect.

  Further, the acoustic system is installed in a vehicle, and the reference microphone noise correction unit and the correction microphone noise correction unit include a plurality of types of correction filters for use in the filter processing, according to the traveling speed of the vehicle. The type of the correction filter used for the filter processing may be changed.

  In such an acoustic system, by changing the type of the correction filter used for the filter processing according to the traveling speed of the vehicle, the optimum reference frequency corresponding to the frequency characteristics of the reference microphone sound and the correction microphone sound that differ depending on the traveling speed is obtained. Since the correction filter can be selected, it is possible to more appropriately and effectively flatten the frequency characteristics of the reference microphone sound and the correction microphone sound.

  Furthermore, in the acoustic system, the speaker may be a full-range speaker capable of outputting output sound from a low range to a high range.

  As described above, by using a full-range speaker capable of outputting an output sound from a low frequency to a high frequency as the speaker, it is not necessary to use a plurality of speakers such as a low frequency speaker and a high frequency speaker. In this way, the muffler signal of the entire band from the low range to the high range can be output by one speaker, so that the system configuration can be simplified.

  According to the acoustic system of the present invention, since the sound collected by the reference microphone is filtered to flatten the frequency characteristics and then the noise correction processing is performed by the acoustic correction unit, not only the low frequency range. It is possible to obtain a silencing effect by the sound correcting means in the entire band from the low range to the mid-high range.

  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 a vehicle interior, and as shown in FIG. 1, a mute speaker 4L (L speaker) installed on the left and right (left and right facing the front direction) of the headrest portion 3 of the vehicle seat 2. , Silencer speaker 4R (R speaker), error microphone 5L (L microphone, correction microphone), error microphone 5R (R microphone, correction microphone) installed in the vicinity of the silencer speakers 4L, 4R, and the main body of the device that performs noise control And a reference microphone 7 that collects noise (noise, reference microphone sound) to be muffled. The apparatus body 6 is connected to a vehicle speed sensor 9 for detecting the speed of the vehicle, and the vehicle speed sensor 9 can acquire vehicle speed information.

  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 this way, by using full-range speakers as the mute speakers 4L and 4R, it is not necessary to use a plurality of speakers such as a low-frequency speaker and a high-frequency speaker, so that the system configuration can be simplified. .

  The error microphones 5L and 5R are also installed in the headrest portion 3, and are seated on the seat 2 in order to obtain correction data (correction sound, correction microphone sound) for mute processing in the vicinity of the user's left and right ear positions. It is provided in the vicinity of the user's left and right ear positions. 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. As described above, the error microphone 5L and the mute speaker 4L are arranged in the upper left part of the seat 2, and the error microphone 5R and the mute speaker 4R are arranged in the upper right part of the seat 2, so that the user can effectively mute the sound. It can be enjoyed.

  The reference microphone 7 is installed, for example, in the engine room, the trunk room, near the feet of the front seat of the passenger compartment, in the vicinity of the tire mounting position, etc., in order to collect noise to be silenced. For example, when the acoustic system according to the present embodiment is installed for the purpose of silencing the engine drive sound, the reference microphone 7 is disposed in the engine room, and the engine drive sound is collected 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 body 6 includes an L-channel ANC unit (L-channel acoustic correction means) 11, an R-channel ANC unit (R-channel acoustic correction means) 12, and a reference microphone noise correction. Unit (reference microphone noise correction unit) 13, L microphone noise correction unit (L microphone noise correction unit) 14, R microphone noise correction unit (R microphone noise correction unit) 15, and L speaker correction Section 16 and an R speaker correction section 17.

  In addition, a vehicle speed sensor 9 provided in the vehicle is connected to the apparatus body 6, and the reference microphone noise correction unit 13, the L microphone noise correction unit 14, and the R microphone noise correction unit 15 are vehicle speed sensors. By receiving the vehicle speed information from 9, the vehicle speed can be determined in real time.

  The L-channel ANC unit 11 can cancel (mute) the sound (noise) collected by the reference microphone 7 based on the acoustic signal (error signal) collected by the error microphone 5L. Has a role to generate. It is possible to mute the noise by creating a sound having an opposite phase to the noise collected by the reference microphone 7 and superimposing the sound on the L channel ANC unit 11.

  Similarly, the R channel ANC unit 12 can cancel (mute) the sound (noise) collected by the reference microphone 7 based on the acoustic signal collected by the error microphone 5R. Is generated. As an ANC processing algorithm, a known algorithm such as Filtered-x LMS (LMS: least mean square) or Filtered-reference LMS can be used.

  The L channel ANC unit 11 receives an error signal whose frequency characteristics have been flattened by an L microphone noise correction unit 14 (to be described later), and the R channel ANC unit 12 has an R microphone (to be described later). In the noise correction unit 15, an error signal whose frequency characteristic is corrected to be flat is input. In addition, a noise signal whose frequency characteristics have been flattened by a reference microphone noise correction unit 13 (described later) is input to the L channel ANC unit 11 and the R channel ANC unit 12 as noise.

  FIG. 3 is a block diagram showing a schematic configuration of the L-channel ANC unit 11. As shown in FIG. 3, the L channel ANC unit 11 includes a delay unit 20, an acoustic correction unit 21, an LMS unit 22, an FIR filter unit 23, and a multiplication unit 24. The configuration of the R channel ANC unit 12 is the same as that of the L channel ANC unit 11 shown in FIG.

  The delay unit 20 considers the delay time from the mute speaker 4L (or mute speaker 4R) to the error microphone 5L (or error mike 5R), the response time of the mute speaker 4L (or mute speaker 4R), etc. 7 for delaying the sound signal collected by the sound signal 7.

  The acoustic correction unit 21 is provided to correct acoustic characteristics from the mute speaker 4L (or mute speaker 4R) to the error microphone 5L (or error microphone 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 the 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 acoustic characteristic between the mute speaker 4L and the error microphone 5L is C11, and the sound between the mute speaker 4R and the error microphone 5L when the sound of the mute speaker 4R is transmitted to the error microphone 5L installed on the left side of the user U C12, and the sound characteristics between the mute speaker 4L and the error microphone 5R when the sound of the mute speaker 4L is transmitted to the error microphone 5R installed on the right side of the user U is C21. The acoustic characteristic between the mute speaker 4R and the error microphone 5R when the sound is transmitted to the error microphone 5R installed on the right side of the user U is C22. To.

  In this case, the acoustic characteristics of the error microphone 5L and the error microphone 5R in the mute speaker 4L are as shown in FIG. 4B, and the acoustic characteristics of the error microphone 5L and the error microphone 5R in the mute speaker 4R are shown in FIG. ).

  In the acoustic correction unit 21 of the L channel ANC unit 11, an acoustic signal (acoustic signal of the reference microphone 7 subjected to delay processing by the delay unit 20) based on the acoustic characteristics of the mute speaker 4 </ b> L shown in FIG. In addition, the acoustic correction unit 21 of the R channel ANC unit 12 performs acoustic correction processing on the acoustic signal based on the acoustic characteristics of the mute speaker 4R shown in FIG. It will be.

  However, as apparent from FIG. 4B, the level of the acoustic characteristic C11 of the sound transmitted from the mute speaker 4L to the error microphone 5L installed on the left side of the user U is higher than that of the mute speaker 4L. The value is higher than the level of the acoustic characteristic C21 of the sound transmitted to the error microphone 5R installed on the right side. This is because the sound output from the mute speaker 4L is not easily transmitted to the error microphone 5R installed on the right side of the user U by being blocked by the user U's own head. For this reason, in the acoustic correction unit 21 of the L-channel ANC unit 11 shown in the present embodiment, only the acoustic characteristic C11 shown in FIG. 4B is used, and the acoustic signal (the reference subjected to the delay process by the delay unit 20) is used. A sound correction process is performed on the sound signal of the microphone 7.

  Further, as apparent from FIG. 4C, the level of the acoustic characteristic C22 of the sound transmitted from the mute speaker 4R to the error microphone 5R installed on the right side of the user U is higher than that of the mute speaker 4R. The value is higher than the level of the acoustic characteristic C12 of the sound transmitted to the error microphone 5L installed on the left side. Similarly, the sound output from the mute speaker 4R is not easily transmitted to the error microphone 5L installed on the left side of the user U by being blocked by the user U's own head. For this reason, also in the acoustic correction unit of the R channel ANC unit 12 shown in the present embodiment, only the acoustic characteristic C22 shown in FIG. 4C is used, and the acoustic signal (the reference microphone subjected to delay processing by the delay unit) is used. 7) is corrected.

  As described above, in the acoustic correction processing in the acoustic correction unit 21, the level of the acoustic characteristic (cross component) at which the muffler speaker and the error microphone cross each other is low, so the acoustic correction unit is set without considering the cross component. Therefore, it is possible to perform a silence control process that is spatially independent on the left and right.

  The LMS unit 22 performs a least square algorithm based on the acoustic signal collected from the error microphone 5L (or the error microphone 5R) and the acoustic signal of the reference microphone 7 that has been acoustically corrected by the delay unit 20 and the acoustic correction unit 21. The coefficient control of the FIR filter unit 23 is performed.

  The FIR filter is a finite impulse response filter, and the acoustic signal collected by the reference microphone 7 is processed based on the FIR filter unit 23 in which the coefficient control is performed by the LMS unit 22. The output signal processed by the FIR filter unit 23 is inverted in phase by the multiplication unit 24.

  The reference microphone noise correction unit 13 has a role of correcting the frequency of a noise signal to be silenced such as a running noise of a vehicle and an engine sound collected by the reference microphone 7. FIG. 5A illustrates a case where the frequency characteristic example 30 of the noise collected by the reference microphone 7, the frequency characteristic example 31 of the correction filter used for the filter process of the reference microphone noise correction unit 13, and the filter process are applied. This shows a frequency characteristic example 32 of noise. 5A and 5B show linear frequency characteristics for convenience of explanation, but in reality, as shown in FIGS. 7B, 8A, and 8B described later. The frequency characteristics of a non-linear shape are shown.

  As shown in FIG. 5A, the reference microphone noise correction unit 13 performs a filter process on the noise using a correction filter that is inverse to the frequency characteristic 30 of the noise. By applying a filter process to the noise using a correction filter having such an inverse characteristic, it is possible to correct the noise collected by the reference microphone 7 to a flat frequency characteristic 32. Become.

  Note that the traveling noise, engine sound, and the like collected by the reference microphone 7 have characteristics that the characteristics of the noise change according to the traveling state of the vehicle, more specifically, the traveling speed of the vehicle. 6A shows an example of noise frequency characteristics when the vehicle speed is 0 km / h (so-called idling state), and FIG. 6B shows an example of noise frequency characteristics when the vehicle speed is 50 km / h. FIG. 7A shows an example of frequency characteristics of noise when the vehicle speed is 100 km / h.

  As is clear from FIGS. 6A, 6B, and 7A, the level value [dB] of noise corresponds to a level value in the corresponding frequency range that is substantially proportional to the vehicle speed. Show the trend. For this reason, the reference microphone noise correction unit 13 records a plurality of correction filters having frequency characteristics as schematically shown in FIG. 5B, and records the vehicle speed information obtained from the vehicle speed sensor 9. Based on this, a correction filter is selected and determined, and a filter process is performed on noise collected by the reference microphone 7 using the selected and determined correction filter.

  Thus, by determining the correction filter used for the filter process according to the traveling speed of the vehicle, it is possible to more appropriately and effectively flatten the frequency characteristic of the noise subjected to the filter process. The acoustic signal flattened by the reference microphone noise correction unit 13 is output to the L channel ANC unit 11 and the R channel ANC unit 12 as a noise signal.

  FIG. 7B shows the noise collected by the reference microphone 7 and the frequency characteristic example 35 before the correction process (filter correction process) is performed by the reference microphone noise correction unit 13 and the reference microphone noise. It is the figure which showed the frequency characteristic example 36 after the correction process (filter correction process) in the correction | amendment part 13 was made. As is apparent from FIG. 7B, the noise shown in the frequency characteristic example 35 is filtered by the reference microphone noise correction unit 13, thereby maintaining the level value increase / decrease characteristic for each frequency. As shown in the frequency characteristic example 36, the noise frequency characteristic example 35 can be flattened.

  The L microphone noise correction unit 14 performs a filtering process on the error sound (corrected microphone sound) collected by the error microphone 5L before the mute processing is performed in the L channel ANC unit 11 (while it is not performed). Has a role to apply. By applying a filter process to the error sound collected by the error microphone 4L, the frequency characteristics of the error sound can be corrected to a flat state.

  Similarly to the reference microphone noise correction unit 13, the L microphone noise correction unit 14 also records a plurality of correction filters according to the traveling speed of the vehicle, and is based on vehicle speed information acquired from the vehicle speed sensor 9. A correction filter is selected and determined, and a filter process is performed on the error sound collected from the error microphone 5L using the selected and determined correction filter.

  FIG. 8A is a diagram showing the frequency characteristics of the error sound collected by the error microphone 5L, and is an example of the frequency characteristics before the correction process (filter correction process) is performed by the L microphone noise correction unit 14. 37 and a frequency characteristic example 38 after the correction process (filter correction process) is performed in the L microphone noise correction unit 14. As is clear from FIG. 8 (a), the error sound shown in the frequency characteristic example 37 is filtered by the L microphone noise correction unit 14, thereby maintaining the level value increase / decrease state for each frequency. As shown in the frequency characteristic example 38, the noise frequency characteristic example 37 can be flattened.

  Similarly, the R microphone noise correction unit 15 performs a filtering process on the error sound collected by the error microphone 5R before the mute processing is performed in the R channel ANC unit 12 (while it is not performed). Have a role. By applying a filter process to the error sound collected by the error microphone 5R, the frequency characteristic of the error sound can be corrected to a flat state.

  Similarly to the reference microphone noise correction unit 13 and the L microphone noise correction unit 14, the R microphone noise correction unit 15 records a plurality of correction filters according to the traveling speed of the vehicle, and is acquired from the vehicle speed sensor 9. The correction filter is selected / determined based on the vehicle speed information, and the filter processing is performed on the error sound collected from the error microphone R using the selected / determined correction filter.

  FIG. 8B is a diagram showing the frequency characteristics of the error sound collected by the error microphone 5R, and the frequency characteristics before the correction process (filter correction process) is performed by the R microphone noise correction unit 15. An example 39 and a frequency characteristic example 40 after the correction process (filter correction process) is performed in the R microphone noise correction unit 15 are shown. As is clear from FIG. 8 (b), the error sound shown in the frequency characteristic example 39 is filtered by the R microphone noise correction unit 15 to maintain the level value increase / decrease state for each frequency. As shown in the frequency characteristic example 40, the noise frequency characteristic example 39 can be flattened.

  The L speaker correction unit 16 prevents the frequency characteristics of the mute signal from changing according to the characteristics of the mute speaker 4L when the mute signal subjected to the mute process by the L channel ANC unit 11 is output from the mute speaker 4L. In addition, it has a role of performing a correction process on the mute signal. The L speaker correction unit 16 outputs a mute signal without being affected by the characteristics of the muffler speaker 4L by performing a correction process on the mute signal so as to have an opposite phase to the frequency characteristic of the mute speaker 4L. It becomes possible.

  The L speaker correction unit 16 shown in the present embodiment performs a mute signal correction process using the correction characteristics of the speaker as shown in FIG. The correction characteristic of the speaker shown in FIG. 9A is a characteristic that amplifies a level value near 120 Hz by about 10 dB and attenuates a level value near 500 Hz by about 6 dB.

  FIG. 9B shows a frequency characteristic example 41 of the mute signal immediately after the filter processing is performed by the L channel ANC unit 11 (that is, before performing the correction processing by the L speaker correction unit 16), and for the L speaker. It is the graph which showed the frequency characteristic example 42 after performing the correction process by the correction | amendment part 16. FIG. The frequency characteristic example 42 after the correction processing by the L speaker correction unit 16 is amplified by about 10 dB in the level value near 120 Hz, and near 500 Hz, compared with the frequency characteristic example 41 before the correction processing is performed. Is attenuated by about 6 dB, and the frequency characteristic having the correction characteristic of the speaker shown in FIG. 9A is obtained.

  Similarly, when the mute signal subjected to mute processing by the R channel ANC unit 12 is output from the mute speaker 4R, the frequency characteristic of the mute signal is also corresponding to the characteristic of the mute speaker 4R. In order not to change, it has a role of performing a correction process on the mute signal. The R speaker correction unit 17 outputs a mute signal without being affected by the frequency characteristic of the muffler speaker 4R by performing a correction process on the mute signal so as to have an opposite phase to the frequency characteristic of the mute speaker 4R. Is possible.

  In the R speaker correction unit 17 shown in the present embodiment, similarly to the L speaker correction unit 16, correction processing corresponding to the correction characteristics of the R speaker is performed on the mute signal.

  The result of performing the silencing process using the acoustic system 1 based on the configuration described above will be described with reference to the drawings.

  FIG. 10 illustrates an L channel ANC unit 11 and an R channel ANC unit 12 in an acoustic system in which the reference microphone noise correction unit 13, the L microphone noise correction unit 14, and the R microphone noise correction unit 15 are not provided. Example of frequency characteristics in the vicinity of error microphone 5L and error microphone 5R (ANC ON shown in FIG. 10) when operated, and when L channel ANC unit 11 and R channel ANC unit 12 are not operated (that is, mute) An example of frequency characteristics (ANC OFF shown in FIG. 10) in the vicinity of the error microphone 5L and the error microphone 5R in the case where the processing is not performed is shown.

  In an acoustic system in which the reference microphone noise correction unit 13, the L microphone noise correction unit 14, and the R microphone noise correction unit 15 are not provided, the mute processing is performed using the L channel ANC unit 11 and the R channel ANC unit 12. When performed, as shown in FIG. 10, it is possible to effectively reduce the noise in the low range (frequency range of 170 Hz or less), but the noise in the middle and high range (frequency range of 170 Hz or more) is sufficient. It shows a tendency that it is not possible to demonstrate a proper silencing process.

  On the other hand, FIG. 11A shows the noise that has been filtered by the reference microphone noise correction unit 13 and the filter processing by the L microphone noise correction unit 14 in the acoustic system 1 according to the present embodiment. An example of frequency characteristics near the error microphone 5L (ANC ON shown in FIG. 11A) when the L channel ANC unit 11 is applied to the error sound, the reference microphone noise correction unit 13, and the L microphone An example of frequency characteristics in the vicinity of the error microphone 5L (ANC OFF shown in FIG. 11A) when the noise correction unit 14 and the L channel ANC unit 11 are not applied (that is, when mute processing is not performed). Show.

  As shown in FIG. 11A, the frequency characteristics of the case where the mute process is performed using the acoustic system 1 according to the present embodiment (ANC ON shown in FIG. 11A) is the case where the mute process is not performed. Compared to the frequency characteristics of (ANC OFF shown in FIG. 11 (a)), the noise level is reduced overall (reduction of about 10 dB) not only in the low range but also in the entire band from the low range to the mid-high range. Is possible.

  Similarly, in FIG. 11B, in the acoustic system 1 according to the present embodiment, the noise subjected to the filtering process by the reference microphone noise correcting unit 13 and the filtering process performed by the R microphone noise correcting unit 15 are performed. An example of frequency characteristics near the error microphone 5R (ANC ON shown in FIG. 11B) when the R channel ANC unit 12 is applied to the error sound, the reference microphone noise correction unit 13, and the R microphone noise An example of frequency characteristics in the vicinity of the error microphone 5R (ANC OFF shown in FIG. 11B) when the correction unit 15 and the R channel ANC unit 12 are not applied (that is, when mute processing is not performed) is shown. ing.

  Also in FIG. 11 (b), the frequency characteristic when the muffling process is performed using the acoustic system 1 according to the present embodiment (ANC ON shown in FIG. 11 (b)) is the case where the muffling process is not performed (FIG. 11B). Compared with the frequency characteristics of ANC OFF shown in Fig. 11 (b), it is possible to reduce the overall noise level (reduction of about 10 dB) not only in the low band but also in the entire band from the low band to the mid-high band. It has become.

  As described above, in the acoustic system 1 according to the present invention, the frequency characteristics of noise input to the L channel ANC unit 11 and the R channel ANC unit 12 are flattened by the reference microphone noise correction unit 13, and the L channel After the frequency characteristics of the error sound input to the ANC unit 11 for R or the ANC unit 12 for R channel are flattened by the noise correction unit 14 for L microphone or the noise correction unit 15 for R microphone, Since the channel ANC unit 12 performs a silencing process, it is possible to perform a silencing process on the entire frequency from low to middle and high frequencies with a constant response time. Noise in the vicinity of the error microphone installation position) can be effectively reduced.

  FIG. 12A illustrates the noise filtered by the reference microphone noise correction unit 13 and the error sound filtered by the L microphone noise correction unit 14 in the acoustic system 1 according to the present embodiment. On the other hand, when the L channel ANC unit 11 is applied, an example of frequency characteristics in the vicinity of the error microphone 5L (L channel ANC ON shown in FIG. 12A) and when the R channel ANC unit 12 is not applied An example of frequency characteristics in the vicinity of the error microphone 5R (that is, when the mute process is not performed) (R channel ANC OFF shown in FIG. 12A) is shown.

  As shown in FIG. 12A, the noise in the vicinity of the user's left ear position (that is, in the vicinity of the installation position of the error microphone 5L) to which the L-channel ANC unit 11 is applied (that is, the muffling process has been performed) Although the noise reduction unit 14 for the L microphone and the ANC unit 11 for the L channel realize the reduction of the noise in the entire band from the low range to the middle and high range, the ANC unit 12 for the R channel is realized. The noise in the vicinity of the user's right ear position (in the vicinity of the installation position of the error microphone 5R) that did not apply (i.e., the mute process was not performed) could hardly achieve the mute effect.

  On the other hand, FIG. 12B shows the noise filtered by the reference microphone noise correcting unit 13 and the filter processing performed by the R microphone noise correcting unit 15 in the acoustic system 1 according to the present embodiment. An example of frequency characteristics near the error microphone 5R (R channel ANC ON shown in FIG. 12B) when the R channel ANC unit 12 is applied to the error sound, and the L channel ANC unit 11 are not applied. FIG. 12 shows an example of frequency characteristics in the vicinity of the error microphone 5L (L channel ANC OFF shown in FIG. 12B) in the case of the case (that is, when the mute process is not performed).

  As shown in FIG. 12 (b), the noise near the right ear position of the user to which the R channel ANC unit 12 is applied (that is, after performing the muffling process) (near the installation position of the error microphone 5R) is the noise for the reference microphone. The functions of the correction unit 13, the R microphone noise correction unit 15, and the R channel ANC unit 12 achieve overall noise reduction over the entire band from low to middle and high frequencies. The noise in the vicinity of the position of the user's left ear (in the vicinity of the position where the error microphone 5L is installed) that did not apply (i.e., the mute process was not performed) could hardly achieve the mute effect.

  As shown in FIGS. 12A and 12B, in the acoustic system 1 according to the present embodiment, the noise correction unit 13 for reference microphones, the noise correction unit for L microphones regarding noise near the left ear of the user. 14 and the L channel ANC unit 11 can effectively mute the sound, and for noise near the right ear of the user, the reference microphone noise correction unit 13, the R microphone noise correction unit 15 and the R channel Since the silencing process can be effectively performed by the ANC unit 12, it is possible to divide the space into left and right and perform independent silencing control near the left and right ears of the user. For this reason, even when there is a difference in the noise at the left and right ear positions, it is possible to reduce the noise from the low range to the mid-high range with high accuracy and efficiency in accordance with each noise.

  The acoustic system according to the present invention has been described in detail 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. Understood.

  For example, in the acoustic system 1 shown in the above embodiment, the reference microphone noise correction unit 13, the L microphone noise correction unit 14, and the R microphone noise correction unit 15 are based on vehicle speed information acquired from the vehicle speed sensor 9. Although a plurality of correction filters are selected and determined, for example, when the acoustic system according to the present invention is used for a vehicle having a high soundproofing effect, the frequency characteristics of noise entering the vehicle interior according to the vehicle speed are Since it may be difficult to change, the filter processing may be performed using the same correction filter regardless of the vehicle speed.

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 reference microphones concerning 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 output sound of the mute speaker 4L, (C) is the figure which showed the acoustic characteristic in the output sound of the muffler speaker 4R. (A) is the frequency characteristic example of the noise collected by the reference microphone, the frequency characteristic example of the correction filter used for the filter processing of the reference microphone noise correction unit, and the frequency characteristic example of the noise subjected to the filter processing. (B) is the figure which showed the example of the frequency characteristic of the correction filter used for the filter process of the noise correction part for reference microphones for every vehicle speed. (A) shows an example of frequency characteristics of noise when the vehicle speed is 0 km / h (so-called idling state), and (b) shows an example of frequency characteristics of noise when the speed of the vehicle is 50 km / h. . (A) shows an example of frequency characteristics of noise when the vehicle speed is 100 km / h, and (b) shows noise collected by the reference microphone, which is filtered by the reference microphone noise correction unit. 2A and 2B show an example of frequency characteristics before the reference signal is generated and an example of frequency characteristics after the filter processing is performed in the reference microphone noise correction unit. (A) is the figure which showed the example of a frequency characteristic of the error sound picked up by the error microphone 5L, Comprising: The example of a frequency characteristic before performing filter processing in the noise correction part for L microphones, and the noise for L microphones FIG. 5B shows an example of frequency characteristics after the filter processing is performed in the correction unit, and FIG. 5B is a diagram showing an example of frequency characteristics of error sound collected by the error microphone 5R, and is an R microphone noise. The frequency characteristic example before filter processing is performed by the correction unit and the frequency characteristic example after filter processing is performed by the R microphone noise correction unit are shown. (A) is the figure which showed the correction characteristic of the speaker applied in the correction | amendment part for L speakers, (b) is the frequency characteristic of the mute signal before performing the correction process by the correction part for L speakers, and L speaker. It is the figure which showed the frequency characteristic after performing the correction process by the correction | amendment part. In an acoustic system that is not provided with a reference microphone noise correction unit, an L microphone noise correction unit, and an R microphone noise correction unit, an error microphone 5L when the L channel ANC unit and the R channel ANC unit are operated. It is the figure which showed the frequency characteristic example near error microphone 5R, and the frequency characteristic example near error microphone 5L and error microphone 5R when the ANC part for L channels and the ANC part for R channels are not operated. (A) is an example of frequency characteristics in the vicinity of the error microphone 5L when the silencing process is performed in the L channel ANC unit, and an example of frequency characteristics in the vicinity of the error microphone 5L when the silencing process is not performed in the L channel ANC unit. (B) is an example of frequency characteristics in the vicinity of the error microphone 5R when the muffling processing is performed in the R channel ANC section, and in the case where the muffling processing is not performed in the R channel ANC section. It is the figure which showed the example of a frequency characteristic near error microphone 5R. (A) is a frequency characteristic example in the vicinity of the error microphone 5L when the muffling process is performed in the L channel ANC section, and a frequency characteristic example in the vicinity of the error microphone 5R when the mute process is not performed in the R channel ANC section. (B) is an example of frequency characteristics in the vicinity of the error microphone 5R when the muffling process is performed in the R channel ANC part, and in the case where the muffling process is not performed in the L channel ANC part. It is the figure which showed the example of the frequency characteristic of error microphone 5L vicinity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Acoustic system 2 ... Seat 3 ... (Seat) headrest part 4L, 4R ... Silent speaker (speaker, L speaker, R speaker)
5L, 5R: Error microphone (correction microphone, L microphone, R microphone)
6 ... device main body part 7 ... reference microphone 8 ... (back) seat back part 9 ... vehicle speed sensor 11 ... L channel ANC part (acoustic correction means, L channel acoustic correction means)
12 ... R channel ANC section (acoustic correction means, R channel acoustic correction means)
13: Reference microphone noise correction section (reference microphone noise correction means)
14 ... L microphone noise correction section (L microphone noise correction means)
15 ... R microphone noise correction section (R microphone noise correction means)
16 ... L speaker correction unit 17 ... R speaker correction unit 20 ... delay unit 21 ... acoustic correction unit 22 ... LMS unit 23 ... FIR filter unit 24 ... multiplication unit

Claims (5)

A reference microphone that picks up the sound to be muted,
A correction microphone provided near the user's ear position;
Noise correction means for reference microphones that applies a filtering process to the acoustic signal of the reference microphone sound collected by the reference microphone to flatten the frequency characteristics of the reference microphone sound;
Noise correction means for correction microphones that filters the acoustic signal of the correction microphone sound collected by the correction microphone to flatten the frequency characteristics of the correction microphone sound;
Based on the acoustic signal of the reference microphone sound filtered by the noise correction means for reference microphone and the acoustic signal of the corrected microphone sound filtered by the correction means for correction microphone, the user's ear position Acoustic correction means for generating an acoustic signal for reducing noise in the vicinity;
A speaker that outputs an output sound of the acoustic signal generated by the acoustic correction means in the vicinity of the user's ear position;
An acoustic system comprising: The correction microphone is
An L microphone provided near the left ear position of the user;
An R microphone provided near the right ear position of the user;
The correction microphone noise correction means includes:
L microphone noise correction means for applying a filtering process to the acoustic signal of the corrected microphone sound collected by the L microphone to flatten the frequency characteristics of the corrected microphone sound;
R microphone noise correcting means for applying a filtering process to the acoustic signal of the corrected microphone sound collected by the R microphone to flatten the frequency characteristics of the corrected microphone sound,
The acoustic correction means includes
Based on the reference microphone sound signal filtered by the reference microphone noise correction means and the corrected microphone sound signal filtered by the L microphone correction means, the user's left ear L channel acoustic correction means for generating an L channel acoustic signal for reducing noise in the vicinity of the position;
Based on the acoustic signal of the reference microphone sound filtered by the noise correcting means for reference microphone and the acoustic signal of the corrected microphone sound filtered by the correcting means for R microphone, the right ear of the user R channel acoustic correction means for generating an R channel acoustic signal for reducing noise in the vicinity of the position;
The speaker is
An L speaker that outputs an output sound of the L channel acoustic signal in the vicinity of the left ear position of the user;
The acoustic system according to claim 1, further comprising: an R speaker that outputs an output sound of the R channel acoustic signal in the vicinity of the right ear position of the user. The said L microphone and the said L speaker are arrange | positioned at the upper left part of the sheet | seat where the said user sits, The said R microphone and the said R speaker are arrange | positioned at the upper right part of the said sheet | seat. Acoustic system. The sound system is installed in the vehicle,
The reference microphone noise correction unit and the correction microphone noise correction unit include a plurality of types of correction filters for use in the filter processing, and the types of the correction filters used in the filter processing according to the traveling speed of the vehicle. The acoustic system according to any one of claims 1 to 3, wherein the sound system is changed.   The acoustic system according to any one of claims 1 to 4, wherein the speaker is a full-range speaker capable of outputting an output sound from a low range to a high range.

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