Audio system

Abstract

The system provides an "audio system" that outputs audio to each user in a way that prevents one user from hearing the music the other user is listening to. [Solution] The system includes a crosstalk detection unit 1 that extracts the component of the second audio signal output to the second seat speaker from the microphone output as a crosstalk signal, a noise detection unit 2 that extracts the component of the microphone output that does not include the component of the second audio signal or the component of the output sound of the first seat speaker but includes a noise component as a noise signal, a band-by-band gain adjustment unit 4 that adjusts the gain of the second audio signal output to the second seat speaker, and a gain calculation unit 3 that calculates the gain adjustment amount of the band-by-band gain adjustment unit 4 based on the magnitudes of the crosstalk signal and the noise signal, so that the level of the crosstalk signal is less than or equal to the level of the noise signal.

Description

Technical Field

[0001] The present invention relates to an audio system.

Background Art

[0002] As a technology for controlling a sound field so that a target sound to be listened to, which is a sound that a user wants to listen to, can be listened to only by the user, while outputting the target sound from a speaker to a first area where the user is located, a technique is known in which a pseudo-noise sound that inhibits the listening of the target sound is output from a speaker to a second area, which is an area where listening of the target sound is to be suppressed, such as an area where others are located (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When different music is listened to by the user in the driver's seat and the user in the passenger seat in an automobile, it is desirable that the music being listened to by one user can be heard by that user, while the music being listened to by the other user cannot be heard. Therefore, it is conceivable to output a pseudo-noise sound that masks the music being listened to by the other user to one user. However, since this pseudo-noise sound is a noise sound that does not originally exist, it deteriorates the noise environment for music listening by one user. Therefore, an object of the present invention is to output music to each user in a form in which the music being listened to by the other user cannot be heard by the one user without deteriorating the noise environment for music listening by the one user.

Means for Solving the Problems

[0005] To achieve the above objectives, the present invention provides a first-seat speaker positioned near the first seat of an automobile, a microphone positioned near the head of a user seated in the first seat, a second-seat speaker positioned near the second seat of an automobile, a first-seat sound source that outputs a first audio signal from the first-seat speaker, a second-seat sound source that outputs a second audio signal, a gain adjustment unit that adjusts the gain of the second audio signal and outputs it to the second-seat speaker, a crosstalk detection unit that extracts the component of the output sound of the second-seat speaker included in the output of the microphone as a crosstalk signal, a noise detection unit that extracts a component in the output of the microphone that does not include the component of the output sound of the first-seat speaker and the component of the output sound of the second-seat speaker as a noise signal, and a gain calculation unit that calculates the amount of gain adjustment of the second audio signal in the gain adjustment unit so that the crosstalk signal is less than the noise signal by a predetermined level. Here, the gain adjustment unit adjusts the gain of the second audio signal by the gain adjustment amount calculated by the gain calculation unit and outputs it to the second seat speaker.

[0006] Alternatively, in this audio system, the crosstalk detection unit may generate the crosstalk signal by removing the noise signal component and the output sound component of the first seat speaker from the output of the microphone, and the noise detection unit may generate the noise signal by removing the output sound component of the first seat speaker and the output sound component of the second seat speaker from the output of the microphone.

[0007] In the audio system described above, the gain calculation unit calculates the gain adjustment amount of the second audio signal in the gain adjustment unit for each predetermined bandwidth such that the crosstalk signal is a predetermined level lower than the noise signal. The gain adjustment unit may adjust the gain of the second audio signal for each of the frequency bands using the gain adjustment amount calculated for that frequency band by the gain calculation unit.

[0008] Furthermore, in the above audio system, one of the first and second seats may be the driver's seat and the other the passenger seat. With such an audio system, the gain of the second audio signal for the second seat can be adjusted to a level inaudible to the first-seat user, while simultaneously suppressing the amount of adjustment to a level where the second audio signal becomes inaudible to the first-seat user due to noise. This ensures that the second-seat user's ability to hear the second audio signal is not hindered as much as possible. [Effects of the Invention]

[0009] As described above, according to the present invention, music can be output to each user in a manner that prevents one user from hearing the music being listened to by the other user, without degrading the noise environment for one user's music listening. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows the configuration of an audio system according to an embodiment of the present invention. [Figure 2] This figure shows an example of the arrangement of a microphone and speaker according to an embodiment of the present invention. [Figure 3] This is a diagram showing the configuration of the crosstalk detection unit according to an embodiment of the present invention. [Figure 4] This figure shows the configuration of the noise detection unit according to an embodiment of the present invention. [Figure 5] This figure shows the configuration of the gain calculation unit and the gain adjustment unit for each bandwidth according to an embodiment of the present invention. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below. Figure 1 shows the configuration of the audio system according to this embodiment. This audio system is designed for use in automobiles and, as shown in the diagram, includes a microphone MC_P for the passenger seat, a speaker SP_P for the passenger seat, and a speaker SP_D for the driver's seat. Here, as shown in Figure 2, the passenger-side microphone MC_P and passenger-side speaker SP_P are positioned near the head of the passenger seat, such as on the passenger-side headrest, while the driver-side speaker SP_D is positioned near the head of the driver seat, such as on the driver-side headrest.

[0012] Returning to Figure 1, the audio system includes a sound source AS_P for the passenger seat and a sound source AS_D for the driver's seat. The audio signal from the passenger seat sound source AS_P is output from the passenger seat speaker SP_P, and the audio signal from the driver's seat sound source AS_D is output from the driver's seat speaker SP_D. Furthermore, this embodiment adjusts the output to the driver's seat speaker SP_D so that the audio signal from the driver's seat sound source AS_D is not audible to the user seated in the passenger seat. The audio system includes a crosstalk detection unit 1, a noise detection unit 2, a gain calculation unit 3, and a gain adjustment unit 4 for each frequency band. The gain adjustment unit 4 for each frequency band is a so-called equalizer, and for each 1 / 3 octave band, it adjusts the gain of the audio signal of the driver's seat sound source AS_D according to the gain control signal G output by the gain calculation unit 3, and outputs it to the driver's seat speaker SP_D. The crosstalk detection unit 1 uses the output of the passenger-side microphone MC_P as the microphone input signal Min and the output of the driver-side speaker SP_D as SP_OUT_D, and extracts the component of the speaker SP_D output SP_OUT_D from the microphone input signal Min as the crosstalk signal CT. The noise detection unit 2 uses the output of the passenger-side speaker SP_P as SP_OUT_P and extracts the components of the microphone input signal Min, excluding the components of the output of speaker SP_D (SP_OUT_D) and the output of speaker SP_P (SP_OUT_P), as the noise signal NZ. In this case, the noise signal NZ primarily contains environmental noise components that do not involve the audio system, such as road noise. The gain calculation unit 3 calculates, for each 1 / 3 octave band, the excess of the level of the crosstalk signal CT over the level of the noise signal NZ, and calculates the gain of the per-band gain adjustment unit 4 that attenuates the audio signal of the sound source AS_D for the driver's seat. Then, the gain calculation unit 3 outputs a gain control signal G that controls the gain of the per-band gain adjustment unit 4 according to the calculated gain.

[0013] Next, the configuration of the crosstalk detection unit 1 is shown in FIG. 3. As shown in the figure, the crosstalk detection unit 1 includes a first adaptive filter 11, a first adder 12, a second adaptive filter 13, and a second adder 14. The first adaptive filter 11 is an adaptive filter that takes the noise signal NZ as an input. The first adder 12 subtracts the output of the first adaptive filter 11 from the microphone input signal Min and outputs the result. Then, the first adaptive filter 11 sets its transfer function (filter coefficients) so that the output of the first adder 12 becomes minimum. Therefore, the output of the first adder 12 is a signal obtained by removing the component of the noise signal NZ from the microphone input signal Min. Next, the second adaptive filter 13 is an adaptive filter that takes the output SP_OUT_P of the speaker SP_P for the passenger seat as an input. The second adder 14 subtracts the output of the second adaptive filter 13 from the output of the first adder 12 and outputs the result. Then, the second adaptive filter 13 sets its transfer function (filter coefficients) so that the output of the second adder 14 becomes minimum. Therefore, the output of the second adder 14 is a signal obtained by removing the component of the noise signal NZ and the component of the output signal SP_OUT_P (the output component of the speaker SP_P for the passenger seat) from the microphone input signal Min, that is, a signal representing the crosstalk component (crosstalk) of the output of the speaker SP_D for the driver's seat in the microphone input signal Min. This signal is output as the crosstalk signal CT.

[0014] Next, the configuration of the noise detection unit 2 is shown in FIG. 4. As shown in the figure, the noise detection unit 2 includes a third adaptive filter 21, a third adder 22, a fourth adaptive filter 23, and a fourth adder 24. The third adaptive filter 21 is an adaptive filter that takes the output SP_OUT_P of the speaker SP_P for the passenger seat as an input, and the third adder 22 subtracts the output of the third adaptive filter 21 from the microphone input signal Min and outputs the result. Then, the third adaptive filter 21 sets its transfer function (filter coefficients) so that the output of the third adder 22 is minimized. Therefore, the output of the third adder 22 becomes a signal obtained by removing the component of the output SP_OUT_P of the speaker SP_P for the passenger seat from the microphone input signal Min. Next, the fourth adaptive filter 23 is an adaptive filter that takes the output SP_OUT_D of the driver's seat speaker SP_D as an input, and the fourth adder 24 subtracts the output of the fourth adaptive filter 23 from the output of the third adder 22 and outputs the result. Then, the fourth adaptive filter 23 sets its transfer function (filter coefficients) so that the output of the fourth adder 24 is minimized. Therefore, the output of the fourth adder 24 is a signal obtained by removing, from the microphone input signal Min, the component of the output signal SP_OUT_P (the output component of the speaker SP_P for the passenger seat) and the crosstalk component (crosstalk) of the output of the driver's seat speaker SP_D. That is, it is a signal representing the noise component in the microphone input signal Min, and this signal is output as the noise signal NZ.

[0015] Next, FIG. 5 shows the configurations of the gain calculation unit 3 and the per-band gain adjustment unit 4. As shown in the figure, the gain calculation unit 3 includes a noise band division unit 31, a noise power calculation unit 32, a crosstalk band division unit 33, a crosstalk power calculation unit 34, and a gain calculation unit 35. The noise band division unit 31 divides the noise signal NZ into 1 / 3 octave bands, and the noise power calculation unit 32 calculates the power of the noise signal NZ for each divided band. The crosstalk band division unit 33 divides the crosstalk signal CT into 1 / 3 octave bands, and the crosstalk power calculation unit 34 calculates the power of the crosstalk signal CT for each divided band. The gain calculation unit 35 calculates the gain of the band-by-band gain adjustment unit 4 so that, for each band, the audio signal SP_OUT_D output by the band-by-band gain adjustment unit 4 is attenuated by the amount by which the power of the crosstalk signal CT exceeds the power of the noise signal NZ, plus a margin; that is, so that the power of the crosstalk signal CT is below the power of the noise signal NZ by a predetermined level, and outputs this as a gain control signal G to the band-by-band gain adjustment unit 4. More specifically, for each band, the gain calculation unit 35 calculates the gain of the band-by-band gain adjustment unit 4 so that, for each band, the audio signal SP_OUT_D output by the band-by-band gain adjustment unit 4 is attenuated by the amount by which the power of the crosstalk signal CT exceeds the power of the noise signal NZ; that is, so that the power of the crosstalk signal CT is less than or equal to the power of the noise signal NZ, and outputs this as a gain control signal G to the band-by-band gain adjustment unit 4.

[0016] However, the gain calculation unit 35 calculates a gain with zero attenuation for bandwidths where the power of the crosstalk signal CT is lower than the power of the noise signal NZ. Alternatively, multiple gain sets for each frequency band may be prepared in advance, and the set with the minimum attenuation, where the power of the crosstalk signal CT is lower than the power of the noise signal NZ in all frequency bands, can be selected and used as the gain control signal G. Furthermore, a lower limit may be set for each bandwidth in the gain calculation unit 35. Next, the band-by-band gain adjustment unit 4 includes a band division unit 41, a gain adjustment unit 42, and a band combination unit 44. The mask noise band division unit divides the audio signal of the driver's seat sound source AS_D into 1 / 3 octave bands. The gain adjustment unit adjusts the gain of the audio signal for each divided band according to the gain control signal G input from the gain calculation unit 3. The band synthesis unit 44 synthesizes the adjusted audio signals of each band and outputs them to the driver's seat speaker SP_D.

[0017] Embodiments of the present invention have been described above. Thus, according to this embodiment, the gain of the audio signal output to the driver's seat can be adjusted to a level that is inaudible to the passenger seat user, while keeping the amount of adjustment to a level that is inaudible to the passenger seat user due to noise. Therefore, the driver's seat user's ability to hear the audio signal directed to the driver's seat is not interfered with as much as possible.

[0018] Here, the above describes the case where the output to the driver's speaker SP_D is adjusted so that the audio signal from the driver's seat sound source AS_D is inaudible to the user seated in the passenger seat. However, the audio system may also be equipped with a configuration symmetrical to the above for the passenger and driver seats, so that the output to the passenger seat speaker SP_P is also adjusted so that the audio signal from the passenger seat sound source AS_P is inaudible to the user seated in the driver's seat. Furthermore, the driver's seat and passenger seat in the above embodiments may be replaced with any two seats in the automobile. [Explanation of symbols]

[0019] 1...Crosstalk detection unit, 2...Noise detection unit, 3...Gain calculation unit, 4...Gain adjustment unit for each band, 11...First adaptive filter, 12...First adder, 13...Second adaptive filter, 14...Second adder, 21...Third adaptive filter, 22...Third adder, 23...Fourth adaptive filter, 24...Fourth adder, 31...Noise band division unit, 32...Noise power calculation unit, 33...Crosstalk band division unit, 34...Crosstalk power calculation unit, 35...Gain calculation unit, 41...Band division unit, 42...Gain adjustment unit, 44...Band combination unit.

Claims

1. A first-seat speaker positioned near the first seat of the car, A microphone is positioned near the head of the user seated in the first seat, A second-seat speaker positioned near the second seat of the car, A first-seat sound source that outputs the first audio signal from the first-seat speaker, A sound source for the second seat that outputs a second audio signal, A gain adjustment unit that adjusts the gain of the second audio signal and outputs it to the second seat speaker, A crosstalk detection unit extracts the output sound component of the second speaker included in the output of the microphone as a crosstalk signal. A noise detection unit extracts a component from the output of the microphone that does not contain the output sound component of the first seat speaker or the output sound component of the second seat speaker as a noise signal. The system includes a gain calculation unit that calculates the amount of gain adjustment for the second audio signal in the gain adjustment unit so that the crosstalk signal is less than the noise signal by a predetermined level, The audio system is characterized in that the gain adjustment unit adjusts the gain of the second audio signal by the gain adjustment amount calculated by the gain calculation unit and outputs it to the second seat speaker.

2. The audio system according to claim 1, The audio system is characterized in that the crosstalk detection unit generates the crosstalk signal by removing the noise signal component and the output sound component of the first seat speaker from the output of the microphone.

3. The audio system according to claim 1, The audio system is characterized in that the noise detection unit generates the noise signal by removing the output sound components of the first seat speaker and the output sound components of the second seat speaker from the output of the microphone.

4. The audio system according to claim 1, The crosstalk detection unit generates the crosstalk signal by removing the noise signal component and the output sound component of the first seat speaker from the microphone output. The audio system is characterized in that the noise detection unit generates the noise signal by removing the output sound components of the first seat speaker and the output sound components of the second seat speaker from the output of the microphone.

5. An audio system according to claim 1, 2, 3, or 4, The gain calculation unit calculates the amount of gain adjustment for the second audio signal in the gain adjustment unit for each predetermined bandwidth such that the crosstalk signal is less than the noise signal by a predetermined level. The audio system is characterized in that the gain adjustment unit adjusts the gain of the second audio signal for each of the bandwidths by the gain adjustment amount calculated for that bandwidth by the gain calculation unit.

6. An audio system according to claim 1, 2, 3, or 4, An audio system characterized in that one of the first and second seats is the driver's seat and the other is the passenger seat.

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