The present application claims priority to and incorporates by reference the entire contents of Japanese priority documents 2007-265865 and 2007-265866 filed in Japan on Oct. 11, 2007.
1. Field of the Invention
The present invention relates to an acoustic system for providing an individual acoustic environment with respect to each individual space in a predetermined space, and, more particularly to an acoustic system that can effectively reduce sound leakage from other seats even if there is an environmental change or a change with time, and that can provide an individual acoustic environment with a realistic sense while not blocking visibility of a listener.
2. Description of the Related Art
An acoustic system for providing a different acoustic environment for each seat has been known in vehicles such as airplanes, trains, and cars. However, if a listener does not use a headset, leak sound or noise from other seats causes a problem. Therefore, to provide a comfortable individual acoustic environment, reduction of such noise is important.
For example, Japanese Patent Application Laid-open No. H5-61477 discloses a method of reducing noise by using an error microphone for obtaining noise to generate a control sound for negating the obtained noise. Further, as a method of reducing sound leakage from other seats, Filtered-XLMS (adaptive least mean square filter) that uses an output of an error microphone and an other-seat sound source as a reference signal has been known.
It is assumed here that an other-seat speaker is arranged on other seats and a self seat speaker and a self-seat error microphone are arranged on a self seat. When the Filtered-XLMS is used, a control sound for negating sound leakage is generated based on a leak sound transfer function from the other-seat speaker to the self seat and an error path transfer function between the self seat speaker and the self-seat error microphone. As such an error path transfer function, a function that is presumed in advance prior to provision of the acoustic system is generally used.
However, when the error path transfer function presumed in advance is used, there is a problem that, when a sound field environment is changed between the time of presumption and the time of control, reduction accuracy of the leak sound deteriorates. Specifically, there is a change in the sound field environment (an environmental change such as person's position, humidity, and temperature, and a change with time of the error microphone and the speaker), between the time of presumption of the error path transfer function and the time of control using such an error path transfer function. However, because the path transfer function used at the time of control is not for the sound field environment at the time of control, highly accurate sound-leakage reduction control cannot be performed.
Meanwhile, to improve the control efficiency of the sound-leakage reduction control, it is desired to install a speaker and an error microphone at a position close to ears of a listener. However, when an individual acoustic environment is provided in a car, the speaker and the error microphone need to be installed on a self seat due to a safety reason such as not blocking the visibility of a driver.
However, if the speaker is installed on the self seat, the listener hears the sound from the back, thereby causing a problem such that a sound image is localized at the back, and listening with a realistic sense becomes difficult.
Accordingly, in the case that a speaker is arranged at the back of a listener, it is an important issue how to realize an acoustic system that can effectively reduce sound leakage from other seats even if there is an environmental change or a change with time, and that can provide an individual acoustic environment with a realistic sense while not blocking visibility of a listener.
It is an object of the present invention to at least partially solve the problems in the conventional technology.
According to the present invention, an acoustic system includes: a self speaker that is installed to be at back of a listener in a first individual space in a predetermined space; an error microphone that is installed to be closer to the listener than the self speaker; a sound-leakage reducing unit that generates control sound for negating sound leaked from an other speaker installed in a second individual space in the predetermined space to the first individual space based on a leak sound transfer function between the other speaker and the error microphone and an error path transfer function between the self speaker and the error microphone, and provides the control sound to the self speaker; a virtual sound-source unit that generates a virtual sound source to form a sound image in front of the listener; and a localization correcting unit that corrects rearward localization of the sound image closer to the listener, the sound image being formed by reproduction of the virtual sound source by the self speaker.
The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.
Exemplary embodiments of an acoustic system according to the present invention will be explained in detail below with reference to the accompanying drawings. While the acoustic system according to the present invention is explained below as being applied to a car, it can also be applied to seats in movie theaters, concert halls, trains, buses, and the like.
As illustrated in
Thus, by dynamically presuming the error path transfer function C(z) highly variable according to an environmental change, operation accuracy of the sound-leakage reduction filter 12 can be improved. Further, by generating a sound having a sound image in front of the listener by the virtual sound-source filter 14, and localizing the sound image with the position of the self seat speaker 3 being set as a reference at a position of the self-seat error microphone 4 near the ear position of the listener by the rear-sound-source inverse filter 15, the individual acoustic environment with a realistic sense can be provided.
A conventional acoustic system is explained with reference to
As illustrated in
As illustrated in
That is, the acoustic system 201 according to the conventional technology adaptively controls the sound-leakage reduction filter 212 based on the “error path transfer function Ĉ(z)” presumed in advance and an output of the self-seat error microphone 204. The sound-leakage reduction filter 212 presumes the “leak sound transfer function P(z)” based on the static “error path transfer function Ĉ(z)”.
However, because the “error path transfer function C(z)” changes according to a sound field environment (environment such as person's position, humidity, and temperature, and environment with time of the error microphone and the speaker) at the time of control, the “error path transfer function C(z)” is separated from a static “error path transfer function Ĉ(z)”. Therefore, even if the sound-leakage reduction filter 212 is adaptively controlled by using the error path transfer function 214, with the “error path transfer function Ĉ(z)” being the entity, highly accurate reduction of sound leakage cannot be performed.
In the acoustic system 201 according to the conventional technology, because the self seat speaker 203 installed at the back of the listener on the self seat provides the acoustic environment to the listener on the self seat, the acoustic environment to be provided is localized at the back of the listener. Therefore, there is a problem that an acoustic environment with a realistic sense cannot be provided to the listener.
In the acoustic system 1 according to the first embodiment illustrated in
Returning to the explanation of
The self seat speaker 3 includes a right speaker 3a and a left speaker 3b, and is installed, for example, on a backside of a driver's seat in the car. The self seat speaker 3 is connected to the sound-leakage reduction filter 12 and the rear-sound-source inverse filter 15, to reproduce the individual acoustic environment such as music or voices for the self seat, and reproduce a control sound for negating the leak sound from the other-seat speaker 2.
The self-seat error microphone 4 includes a right error microphone 4a and a left error microphone 4b respectively installed in front of the right speaker 3a and the left speaker 3b constituting the self seat speaker 3. The self-seat error microphone 4 is installed, for example, on the backside of the driver's seat in the car as in the case of the self seat speaker 3. An output of the self-seat error microphone 4 is used for presumption of the “error path transfer function C(z)” in the auxiliary filter 16.
The other-seat sound source 11 is a device that reproduces music or voices recorded on a portable recording medium such as a CD (compact disk) or a DVD (digital versatile disk), or music or voice from radio, television, car navigation system and the like. An output of the other-seat sound source 11 is input to the other-seat speaker 2 and also to the sound-leakage reduction filter 12 and the auxiliary filter 16.
The sound-leakage reduction filter 12 uses the leak sound transfer function P(z) and the error path transfer function C(z) presumed based on the output of the auxiliary filter 16, to generate a control sound for negating the leak sound from the other-seat speaker 2 on the front seat. The sound-leakage reduction filter 12 is configured as the ADF (adaptive digital filter).
A calculation procedure performed by the sound-leakage reduction filter 12 is briefly explained. When it is assumed that the sound-leakage reduction filter 12 is “H1(z)”, the auxiliary filter 16 is “S(z)”, the leak sound transfer function is “P(z)”, and error path transfer function is “C(z)”, relation between these is expressed by an equation “S(z)=P(z)+H1(z)C(z)”. The control sound (negating sound) generated by the sound-leakage reduction filter 12 is expressed as “H1(z)C(z)”.
In the equation “S(z)=P(z)+H1(z)C(z)”, by inputting two initial values (S1(z), H11(z), and S2(z), H12(z)) respectively to S(z) and H1(z), and updating S(z) and H1(z) so that a negating error becomes minimum, optimum P(z) and C(z) can be presumed. An optimum H1(z) is expressed by an equation “H1(z)=−P(z)/C(z)”.
The self-seat sound source 13 is a device that reproduces music or voice recorded on a portable recording medium such as a CD (compact disk) or a DVD (digital versatile disk), or music or voice from radio, television, car navigation system and the like. An output of the self-seat sound source 13 is output to the self seat speaker 3 via the virtual sound-source filter 14 and the rear-sound-source inverse filter 15.
The virtual sound-source filter 14 is a filter (Q(z)) that receives the output from the self-seat sound source 13 to generate a virtual sound field having a virtual sound image in front of the listener on the self seat. The virtual sound field generated by the virtual sound-source filter 14 is obtained, as indicated by the virtual sound source 5 in
The rear-sound-source inverse filter 15 is a filter defined as an inverse function of the error path transfer function C(z) between the self seat speaker 3 and the self-seat error microphone 4, and performs a process of localizing the virtual sound field based on the position of the self seat speaker 3 at a position of the self-seat error microphone 4. Accordingly, rearward localization of the sound image resulting from installation of the self seat speaker 3 at the back of the listener can be corrected. When the rear-sound-source inverse filter 15 is designated as “Hb(z)”, Hb(z) is expressed by an equation “Hb(z)=1/C(z)”. As C(z) in this equation, a static error path transfer function presumed in advance is used.
The auxiliary filter 16 receives the outputs from the other-seat sound source 11 and the self-seat error microphone 4, and performs a process of presuming the leak sound transfer function P(z) and the error path transfer function C(z). An output of the auxiliary filter 16 is used for adaptive control of the sound-leakage reduction filter 12.
A positional relation of the other-seat speaker 2, the self seat speaker 3, and the self-seat error microphone 4 explained with reference to
As illustrated in
Further, the other-seat speaker 2 including the right speaker 2a and the left speaker 2b is installed toward the listener near the head of the listener on a rear seat 102 at the back of the driver's seat. In
The effects of the virtual sound-source filter 14 and the rear-sound-source inverse filter 15 are explained next with reference to
However, although the virtual sound source 5 generated by the virtual sound-source filter 14 has a sound image in front of the listener 111, a reproduction reference position of the sound image is based on a reproduction position with the headset (that is, the ear position) in the case that the listener 111 uses the headset. However, the position of the self seat speaker 3 (see 112 in
The rear-sound-source inverse filter 15 is for correcting such a rearward localization sense, and corrects the reproduction reference position of the sound image from 112 in
A signal flow in the acoustic system 1 according to the first embodiment is explained next with reference to
Further, regarding a self-seat error microphone signal corresponding to the self-seat error microphone 4, a signal from the right error microphone 4a is described as “mER” and a signal from the left error microphone 4b is described as “mEL”. Regarding the self-seat sound source 13, the right signal is described as “mR” and the left signal is described as “mL”, and regarding the other-seat sound source 11, the right signal is described as “oR” and the left signal is described as “oL”. Regarding the output signal to the self seat speaker 3, a signal to the right speaker 3a is described as “mR” and a signal to the left speaker 3b is described as “mL”. Regarding the output signal to the other-seat speaker 2, a signal to the right speaker 2a is described as “oR” and a signal to the left speaker 2b is described as “oL”.
As illustrated in
A signal flow in the localization control 21 is explained first. The signals mR and mL corresponding to the self-seat sound source 13 are input to the virtual sound-source filter 14 via the A/D 30. The virtual sound-source filter 14 converts the signals mR and mL to signals corresponding to the virtual sound field having a virtual sound image in front of the listener on the self seat, and outputs the signals to the rear-sound-source inverse filter 15. The rear-sound-source inverse filter 15 performs a correction process of bringing the rearward localization of the sound image closer to the ear position of the listener.
The output of the rear-sound-source inverse filter 15 is input to the MIX 33 via the EQ 21a and the VOL 31. The MIX 33 synthesizes the signals mR and mL converted in the localization control 21 with the signals oR and oL converted in the sound-leakage reduction control 22 (control sound, which is a negating sound of the leak sound), and outputs the synthesized signals to the self seat speaker 3 via the D/A 33 as the signals mR and mL.
A signal flow in the sound-leakage reduction control 22 is explained next. The signals oR and oL corresponding to the other-seat sound source 11 are input to the Spread 22a via the A/D 30. The Spread 22a distributes the signals oR and oL to a Down Sample FIR filter 22b and a Delay 22c.
The Delay 22c having received the signals oR and oL distributed by the Spread 22a performs a predetermined delay process with respect to these signals, and outputs the signals to the other-seat speaker via the VOL 32 and the D/A 34 as the signals oR and oL.
Meanwhile, mER and mEL, which are self-seat error microphone signals via the A/D 30, are also input to the Down Sample FIR filter 22b having received the signals oR and oL distributed by the Spread 22a. The Down Sample FIR filter 22b performs resampling (down-sampling) by a sampling frequency lower than the sampling frequency of the input signal. The signal down-sampled by the Down Sample FIR filter 22b is up-sampled in an Up Sample FIR filter 22h and output. Thus, by using the down-sampling and the up-sampling together, the leak sound can be reduced highly accurately, as compared with a case that only a sound in a predetermined frequency range is reduced by using a low-pass filter or the like.
The signals oR and oL output from the Down Sample FIR filter 22b are input to the auxiliary filter 16 and the sound-leakage reduction filter 12. The signals oR and oL output from the auxiliary filter 16 are input to an ADF-S-Calc 22d together with the signals mER and mEL output from the Down Sample FIR filter 22b, thereby calculating a value S(z) of the auxiliary filter 16 in the ADF-S-Calc 22d.
A coefficient value group calculated by the ADF-S-Calc 22d is output to the sound-leakage reduction filter 12 via the FFT 22e, an H1 Calc 22f, and the IFFT 22g. The H1 Calc 22f calculates a value H1(z) of the sound-leakage reduction filter 12.
An output signal from the IFFT 22g and signals oR and oL from the Down Sample FIR filter 22b are input to the sound-leakage reduction filter 12. The control sound (negating sound of the leak sound) calculated by the sound-leakage reduction filter 12 is output to the MIX 33 via the Up Sample FIR filter 22h and the VOL 32, synthesized with the signals mR and mL converted in the localization control 21 by the MIX 33, and output to the self seat speaker 3 via the D/A 34 as the signals mR and mL.
As described above, according to the first embodiment, the acoustic system is configured such that the sound-leakage reduction filter generates a control sound for negating the sound leaked from the other speaker installed in a second individual space toward a first individual space based on the leak sound transfer function between the other speaker and the error microphone and the error path transfer function between the self speaker and the error microphone, by using the self speaker installed at the back of the listener in the first individual space and the error microphone installed closer to the listener than the self speaker, and provides the generated control sound to the self speaker. The virtual sound-source filter generates a virtual sound source, which is a sound provided by arranging a sound image in front of the listener, and the rear-sound-source inverse filter corrects the rearward localization of the sound image generated by reproduction of the virtual sound source by the self speaker closer to the listener.
Further, the acoustic system is configured such that the auxiliary filter is connected to the error microphone and the sound-leakage reduction filter so that the leak sound transfer function and the error path transfer function presumed dynamically are provided to the sound-leakage reduction filter.
Therefore, even if there is an environmental change and a change with time, leak sound from other seats can be effectively reduced, and an individual acoustic environment can be provided with a realistic sense while not blocking the visibility of the listener.
An acoustic system according to a second embodiment is explained next.
As illustrated in
Thus, by providing the leak sound transfer function P(z) and the error transfer function C(z) dynamically presumed by the auxiliary filter (first auxiliary filter) 16 to the sound-leakage reduction filter 12, and by providing the error transfer function C(z) dynamically presumed by the auxiliary filter (second auxiliary filter) 17 to the rear-sound-source inverse filter 15, the accuracy of the sound-leakage reduction filter 12 and the rear-sound-source inverse filter 15 can be improved.
Further, by generating a sound having a sound image in front of the listener by the virtual sound-source filter 14, and localizing the sound image with the position of the self seat speaker 3 being set as a reference at a position of the self-seat error microphone 4 near the ear position of the listener by the rear-sound-source inverse filter 15, an individual acoustic environment with a realistic sense can be provided.
As explained with reference to
However, because the “error path transfer function C(z)” changes according to the sound field environment (environment such as person's position, humidity, and temperature, and environment with time of the error microphone and the speaker) at the time of control, the “error path transfer function C(z)” is separated from the static “error path transfer function Ĉ(z)”. Therefore, even if the sound-leakage reduction filter 212 is adaptively controlled by using the error path transfer function 214, with the “error path transfer function Ĉ(z)” being the entity, highly accurate reduction of sound leakage cannot be performed.
Further, in the acoustic system 201 according to the conventional technology, because the self seat speaker 203 installed at the back of the listener on the self seat provides the acoustic environment to the listener on the self seat, the acoustic environment to be provided is localized at the back of the listener. Therefore, there is a problem that the acoustic environment with a realistic sense cannot be provided to the listener.
In the acoustic system 1 according to the second embodiment illustrated in
The acoustic system 1 according to the second embodiment is explained in detail. The other-seat speaker 2 includes the right speaker 2a and the left speaker 2b, and is installed, for example, on the backside of the rear seat or the like in the car. The other-seat speaker 2 is connected to the other-seat sound source 11, and reproduces the individual acoustic environment such as music and voices for other seats.
The self seat speaker 3 includes the right speaker 3a and the left speaker 3b, and is installed, for example, on the backside of the driver's seat in the car. The self seat speaker 3 is connected to the sound-leakage reduction filter 12 and the rear-sound-source inverse filter 15, to reproduce the individual acoustic environment such as music or voices for the self seat, and reproduce a control sound for negating the leak sound from the other-seat speaker 2.
The self-seat error microphone 4 includes the right error microphone 4a and the left error microphone 4b respectively installed in front of the right speaker 3a and the left speaker 3b constituting the self seat speaker 3. The self-seat error microphone 4 is installed, for example, on the backside of the driver's seat in the car as in the case of the self seat speaker 3. The output of the self-seat error microphone 4 is used for presumption of the respective transfer functions in the auxiliary filter (first auxiliary filter) 16 and the auxiliary filter (second auxiliary filter) 17.
The other-seat sound source 11 is a device that reproduces music or voices recorded on a portable recording medium such as a CD (compact disk) or a DVD (digital versatile disk), or music or voice from radio, television, car navigation system and the like. The output of the other-seat sound source 11 is input to the other-seat speaker 2 and also to the sound-leakage reduction filter 12 and the auxiliary filter (first auxiliary filter) 16.
The sound-leakage reduction filter 12 uses the leak sound transfer function P(z) and the error path transfer function C(z) presumed based on the output of the auxiliary filter (first auxiliary filter) 16, to generate the control sound for negating the leak sound from the other-seat speaker 2 on the front seat. The sound-leakage reduction filter 12 is configured as the ADF (adaptive digital filter).
The calculation procedure performed by the sound-leakage reduction filter 12 is briefly explained. When it is assumed that the sound-leakage reduction filter 12 is “H1(z)”, the auxiliary filter 16 is “S(z)”, the leak sound transfer function is “P(z)”, and the error path transfer function is “C(z)”, the relation between these is expressed by the equation “S(z)=P(z)+H1(z)C(z)”. The control sound (negating sound) generated by the sound-leakage reduction filter 12 is expressed as “H1(z)C(z)”.
In the equation “S(z)=P(z)+H1(z)C(z)”, by inputting two initial values (S1(z), H11(z), and S2(z), H12(z)) respectively to S(z) and H1(z), and updating S(z) and H1(z) so that the negating error becomes minimum, optimum P(z) and C(z) can be presumed. The optimum H1(z) is expressed by the equation “H1(z)=−P(z)/C(z)”.
The self-seat sound source 13 is a device that reproduces music or voice recorded on a portable recording medium such as a CD (compact disk) or a DVD (digital versatile disk), or music or voice from radio, television, car navigation system and the like. The output of the self-seat sound source 13 is output to the self seat speaker 3 via the virtual sound-source filter 14 and the rear-sound-source inverse filter 15.
The virtual sound-source filter 14 is a filter (Q(z)) that receives the output from the self-seat sound source 13 to generate the virtual sound field having the virtual sound image in front of the listener on the self seat. The virtual sound field generated by the virtual sound-source filter 14 is obtained, as indicated by the virtual sound source 5 in
The rear-sound-source inverse filter 15 is a filter corresponding to the inverse function of the error path transfer function C(z) between the self seat speaker 3 and the self-seat error microphone 4, and performs a process of localizing the virtual sound field based on the position of the self seat speaker 3 at a position of the self-seat error microphone 4. Accordingly, rearward localization of the sound image resulting from installation of the self seat speaker 3 at the back of the listener can be corrected. When the rear-sound-source inverse filter 15 is designated as “Hb(z)”, Hb(z) is expressed by the equation “Hb(z)=1/C(z)”. C(z) in this equation is dynamically presumed by the auxiliary filter (second auxiliary filter) 17.
The auxiliary filter (first auxiliary filter) 16 receives the outputs from the other-seat sound source 11 and the self-seat error microphone 4, and performs a process of presuming the leak sound transfer function P(z) and the error path transfer function C(z). The output of the auxiliary filter 16 is used for adaptive control of the sound-leakage reduction filter 12.
The auxiliary filter (second auxiliary filter) 17 receives the outputs from the virtual sound-source filter 14 and the self-seat error microphone 4, and performs a process of presuming the error path transfer function C(z).
The output of the auxiliary filter (second auxiliary filter) 17 is used for adaptive control of the rear-sound-source inverse filter 15.
The signal flow in the acoustic system 1 according to the second embodiment is explained next with reference to
Further, regarding the self-seat error microphone signal corresponding to the self-seat error microphone 4, a signal from the right error microphone 4a is described as “mER” and a signal from the left error microphone 4b is described as “mEL”. Regarding the self-seat sound source 13, the right signal is described as “mR” and the left signal is described as “mL”, and regarding the other-seat sound source 11, the right signal is described as “oR” and the left signal is described as “oL”. Regarding the output signal to the self seat speaker 3, a signal to the right speaker 3a is described as “mR” and a signal to the left speaker 3b is described as “mL”. Regarding the output signal to the other-seat speaker 2, a signal to the right speaker 2a is described as “oR” and a signal to the left speaker 2b is described as “oL”.
As illustrated in
The signal flow in the localization control 21 is explained first. The signals mR and mL corresponding to the self-seat sound source 13 are input to the virtual sound-source filter 14 via the A/D 30. The virtual sound-source filter 14 converts the signals mR and mL to signals corresponding to the virtual sound field having a virtual sound image in front of the listener on the self seat, and outputs the signals to the rear-sound-source inverse filter 15 and a Delay 21b as a delay device. The rear-sound-source inverse filter 15 performs a correction process of bringing the rearward localization of the sound image closer to the ear position of the listener. On the other hand, the Delay 21b performs a predetermined delay process to the signals mR and mL and output these signals to the auxiliary filter (second auxiliary filter) 17.
The output of the rear-sound-source inverse filter 15 is input to the MIX 33 via the EQ 21a and the VOL 31. The MIX 33 synthesizes the signals mR and mL converted in the localization control 21 with the signals oR and oL converted in the sound-leakage reduction control 22 (control sound, which is a negating sound of the leak sound), and outputs the synthesized signals to the self seat speaker 3 via the D/A 33 as the signals mR and mL.
The signals oR and oL output from the auxiliary filter (second auxiliary filter) 17 are input to an ADF-S2-Calc 21d together with the signals mER and mEL distributed by the Spread 21b and the ADF-S2-Calc 21d calculates a value S2(z) of the auxiliary filter (second auxiliary filter) 17.
A coefficient value group calculated by the ADF-S2-Calc 21d is output to the rear-sound-source inverse filter 15 via the FFT 21d, an ADF-Hb-Calc 21f, and the IFFT 21g. The ADF-Hb-Calc 21f calculates a value Hb(z) of the rear-sound-source inverse filter 15, that is, an inverse function of the error path transfer function C(z).
The signal flow in sound-leakage reduction control 22 is explained next. The signals oR and oL corresponding to the other-seat sound source 11 are input to the Spread 22a via the A/D 30. The Spread 22a distributes the signals oR and oL to the Down Sample FIR filter 22b and the Delay 22c.
The Delay 22c having received the signals oR and oL distributed by the Spread 22a performs a predetermined delay process with respect to these signals, and outputs the signals to the other-seat speaker via the VOL 32 and the D/A 34 as signals oR and oL.
On the other hand, mER and mEL, which are the self-seat error microphone signals via the A/D 30, are also input to the Down Sample FIR filter 22b having received the signals oR and oL distributed by the Spread 22a. The Down Sample FIR filter 22b performs resampling (down-sampling) by using a sampling frequency lower than the sampling frequency of the input signals. The signals down-sampled by the Down Sample FIR filter 22b are up-sampled in the Up Sample FIR filter 22h and output. Thus, by using the down-sampling and the up-sampling together, the leak sound can be reduced highly accurately compared with a case that only the sound in the predetermined frequency range is reduced by using a low-pass filter or the like.
The signals oR and oL output from the Down Sample FIR filter 22b are input to the auxiliary filter (first auxiliary filter) 16 and the sound-leakage reduction filter 12. The signals oR and oL output from the auxiliary filter (first auxiliary filter) 16 are input to an ADF-S1-Calc 22d together with the signals mER and mEL output from the Down Sample FIR filter 22b, thereby calculating a value S1(z) of the auxiliary filter (first auxiliary filter) 16 in the ADF-S1-Calc 22d.
The coefficient value group calculated by the ADF-S1-Calc 22d is output to the sound-leakage reduction filter 12 via the FFT 22e, an ADF-H1-Calc 22f, and the IFFT 22g. The ADF-H1-Calc 22f calculates the value H1(z) of the sound-leakage reduction filter 12.
An output signal from the IFFT 22g and signals oR and oL from the Down Sample FIR filter 22b are input to the sound-leakage reduction filter 12. The control sound (negating sound of the leak sound) calculated by the sound-leakage reduction filter 12 is output to the MIX 33 via the Up Sample FIR filter 22h and the VOL 32, synthesized with the signals mR and mL converted in the localization control 21 by the MIX 33, and output to the self seat speaker 3 via the D/A 34 as the signals mR and mL.
As described above, according to the second embodiment, the acoustic system is configured such that the sound-leakage reduction filter generates a control sound for negating the sound leaked from the other speaker installed in the second individual space toward the first individual space based on the leak sound transfer function between the other speaker and the error microphone and the error path transfer function between the self speaker and the error microphone, by using the self speaker installed at the back of the listener in the first individual space and the error microphone installed closer to the listener than the self speaker, and provides the generated control sound to the self speaker. The virtual sound-source filter generates the virtual sound source, which is a sound provided by arranging a sound image in front of the listener, and the rear-sound-source inverse filter corrects the rearward localization of the sound image generated by reproduction of the virtual sound source by the self speaker closer to the listener. The first auxiliary filter connected to the error microphone and the sound-leakage reduction filter provides the leak sound transfer function and the error path transfer function presumed dynamically to the sound-leakage reduction filter, and the second auxiliary filter connected to the error microphone and the rear-sound-source inverse filter provides the dynamically presumed error path transfer function to the rear-sound-source inverse filter.
Therefore, even if there is an environmental change and a change with time, leak sound from other seats can be effectively reduced, and the sound source can be stably localized frontwise. Further, it is possible to provide an individual acoustic environment with a realistic sense while not blocking the visibility of a listener.
As described above, the acoustic system according to the present invention is useful for providing an individual acoustic environment with respect to each individual space provided in a predetermined space, and particularly suitable for providing an individual acoustic environment in a movable vehicle such as a car.
Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
Number | Date | Country | Kind |
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2007-265865 | Oct 2007 | JP | national |
2007-265866 | Oct 2007 | JP | national |