Acoustic device, reproduction method, and program

Abstract

The acoustic device adjusts the playback sound such that the playback sound from the speaker is listened in a predetermined playback area, and the acoustic device adjusts the playback sound on the basis of a playback signal output from a source of the playback sound, a detection sound signal indicating a detection sound of a microphone provided close to the speaker, and a transmission characteristic of a sound signal from the speaker to the microphone. A background noise signal indicating ambient sound around a microphone is generated, a sound leakage signal indicating reproduced sound listened to at a representative point is generated on the basis of the transfer characteristics of the reproduced signal and a sound signal from a speaker to the representative point located outside the reproducing area, and the level of the reproduced signal is adjusted. The grade of the sound leakage signal is smaller than that of the background noise signal.

Description

Technical Field

[0001] The present invention relates to a technique for reproducing audio only in the vicinity of a listener. Background Art

[0002] In recent years, directional speakers have been used as audio devices that reproduce music, sounds, etc. only in specific places. Directional speakers are composed of a speaker array in which a plurality of speakers are arranged in a row, as described in Patent Document 1. The directional speaker adjusts the level of the signal reproduced by each speaker for each frequency so that the reproduced sound can be heard only in a preset reproduction area.

[0003] However, in reality, since the reproduced sound also leaks to the non-reproduced area outside the reproduced area, it is difficult to make the reproduced sound level "0" in the non-reproduced area. For this reason, Patent Document 1 describes that when the sound pressure of the reproduced sound leaking to the non-reproduced area exceeds the surrounding noise level, an adjustment is made to narrow the width of the reproduced area. Thus, it is described that the sound pressure of the reproduced sound leaking to the non-reproduced area is suppressed to be lower than the surrounding noise level.

[0004] However, in the technology of Patent Document 1, the width of the reproduction area is adjusted to be narrower when suppressing the sound pressure of the reproduced sound leaking outside the reproduction area. Therefore, there is a concern that people located at the edge of the reproduction area before the adjustment may not be able to hear the reproduced sound normally.

[0005] Prior Art Literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2017-50847 Summary of the invention

[0008] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide a technology that can normally listen to reproduced sound in a reproduction area and can prevent the reproduced sound leaking to the outside of the reproduction area from being recognized.

[0009] Means for solving problems

[0010] An audio device according to one embodiment of the present invention adjusts reproduced sound so that the reproduced sound reproduced by a speaker can be listened to in a given reproduction area, and comprises: a first generating unit that generates a background noise signal representing ambient sound around the microphone based on a reproduced signal output from a sound source of the reproduced sound, a detection sound signal representing detection sound detected by a microphone arranged close to the speaker, and a first characteristic being a transfer characteristic of a sound signal from the speaker to the microphone; a second generating unit that generates a leakage sound signal representing the reproduced sound listened to at a representative point based on the reproduced signal and a second characteristic being a transfer characteristic of a sound signal from the speaker to a representative point outside the reproduction area; and an adjusting unit that adjusts the level of the reproduced signal so that the level of the leakage sound signal is lower than the level of the background noise signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1A It is a plan view showing an example of the structure of the acoustic system according to the first embodiment.

[0012] Figure 1B This is a front view showing an example of the configuration of the acoustic system according to the first embodiment.

[0013] Figure 2 1 is a diagram showing an example of frequency characteristics of reproduced sound and background noise in a non-reproduced area.

[0014] Figure 3 1 is a diagram showing an example of frequency characteristics of reproduced sound and background noise in a non-reproduced area.

[0015] Figure 4 1 is a diagram showing an example of frequency characteristics of reproduced sound and background noise in the reproduction area.

[0016] Figure 5 1 is a diagram showing an example of frequency characteristics of reproduced sound and background noise in the reproduction area.

[0017] Figure 6 This is a diagram showing an example of a detailed configuration of the acoustic system according to the first embodiment.

[0018] Figure 7 This is a flowchart showing an example of signal processing performed in the audio device.

[0019] Figure 8 This is a diagram showing an example of the transfer characteristic from the speaker to the microphone and the transfer characteristic from the speaker to the representative point of the non-reproduction area.

[0020] Fig.9AThis is a diagram showing an example of a difference characteristic between two transfer characteristics and an approximate characteristic thereof.

[0021] Fig. 9B This is a diagram showing an example of a difference characteristic between two transfer characteristics and an approximate characteristic thereof.

[0022] Fig.10 This is a diagram showing an example of a configuration of an acoustic system according to a modification of the first embodiment.

[0023] Fig.11 This is a diagram showing an example of a configuration of an acoustic system according to another modified example of the first embodiment.

[0024] Fig.12 This is a diagram showing an example of a detailed configuration of an acoustic system according to another modification of the first embodiment.

[0025] Fig.13 This is a diagram showing an example of the configuration of an acoustic system according to the second embodiment.

[0026] Fig.14A This is a diagram showing an example of installation positions of a plurality of speakers and a plurality of microphones included in the audio system according to the second embodiment.

[0027] Fig. 14B This is a diagram showing an example of installation positions of a plurality of speakers and a plurality of microphones included in the audio system according to the second embodiment.

[0028] Fig.15A This is a front view showing another example of the installation positions of the plurality of speakers and the plurality of microphones included in the audio system according to the second embodiment.

[0029] Fig. 15B It is a plan view showing another example of the installation positions of the plurality of speakers and the plurality of microphones included in the acoustic system according to the second embodiment.

[0030] Fig.16 This is a diagram showing an example of a detailed configuration of an acoustic system according to the second embodiment.

[0031] Fig.17 This is a diagram showing an example in which the acoustic system according to the second embodiment is applied to three seats.

[0032] Fig.18 FIG. 1 is a diagram showing an example of a configuration of a zone regeneration system according to the prior art. DETAILED DESCRIPTION

[0033] (The process of realizing this disclosure)

[0034] As described above, conventional directional speakers are configured by arranging a plurality of speakers in a row as described in Patent Document 1. Conventional directional speakers adjust the level of a signal reproduced by each speaker for each frequency so that the reproduced sound is heard only in a preset reproduction area.

[0035] exist Fig.18 An example of the structure of a regional regeneration system 1000 according to the prior art is shown. Fig.18 As shown, in the zone reproduction system 1000 , the processing unit 300 performs predetermined signal processing on the audio signal input from the sound source 10 , and outputs the audio signal after the signal processing to the speaker array 9 .

[0036] In the signal processing performed by the processing unit 300, the audio signal input from the sound source 10 is convolved with a control filter for realizing regional reproduction under the reproduction condition specified by the user. The control filter is derived using a given mathematical formula (Formula (7) of Patent Document 1) corresponding to the reproduction condition. The reproduction condition includes the length L of the speaker array 9, the arrangement interval Δx of each speaker 2a to 2h, the number of speakers 2a to 2h provided in the speaker array 9, the distance yref from the speaker array 9 to the reproduction area 100, and the width lb of the reproduction area 100.

[0037] The speaker array 9 reproduces the audio signal after the signal processing by the processing unit 300. As a result, the reproduced sound represented by the audio signal can be clearly heard in the reproduction area 100. However, in reality, the reproduced sound also leaks to the non-reproduction areas 200a and 200b located outside the reproduction area 100. Therefore, it is difficult to make the level of the reproduced sound "0" in the non-reproduction areas 200a and 200b. However, if the reproduced sound leaked to the non-reproduction areas 200a and 200b (hereinafter referred to as leakage sound) is lower than the surrounding noise level, the leakage sound is masked by the surrounding noise and cannot be heard.

[0038] On the other hand, there is a concern that the sound leakage may be heard in the non-reproduction areas 200a and 200b when the ambient noise level decreases during the reproduction of the reproduced sound or the reproduced sound level is set to a high level. That is, since the ambient noise and the reproduced sound level are always changing, there is a concern that the sound leakage may be heard in the non-reproduction areas 200a and 200b when the reproduced sound level becomes relatively high compared to the ambient noise level.

[0039] Therefore, in the technology of Patent Document 1, the ambient noise level is detected by the microphone 3, and when the level of the leaked sound in the non-reproduction area 200a, 200b exceeds the level of the ambient background noise, the width 1b of the reproduction area 100 is adjusted to be narrowed. Thus, the level of the leaked sound is suppressed to be lower than the level of the background noise, and even when the level of the background noise or the reproduced sound changes, the leaked sound is not heard in the non-reproduction area 200a, 200b.

[0040] However, in the technology of Patent Document 1, when suppressing the reproduced sound leaking into the non-reproduced areas 200a and 200b, the width 1b of the reproduced area 100 is adjusted to be narrow. Therefore, there is a concern that a person located at the edge of the reproduced area 100 before the adjustment may not be able to hear the reproduced sound properly.

[0041] Furthermore, the technology of Patent Document 1 does not consider the case where a plurality of sound sources are used to independently listen to the sound of each sound source in a plurality of reproduction areas.

[0042] For example, suppose that multiple passenger seats in trains and airplanes, and multiple seats close to each other such as the driver's seat and the front passenger seat of a car are set as reproduction areas, and the sound of the sound source for each seat is reproduced independently by the speaker arrays set at each seat. In this case, it is necessary to suppress sound leakage between multiple adjacent seats so that the sound reproduced at each seat will not be recognized by the adjacent seats. In addition, in the reproduction of the reproduced sound, since the noise such as driving sound and flying sound and the reproduced sound at each seat will always change, it is also necessary to suppress the sound leakage according to these changes.

[0043] However, such sound leakage suppression control is not described in Patent Document 1. Even if the sound leakage suppression technology of Patent Document 1 is adopted, the width of the reproduction area is adjusted to be narrow, and the range in which the reproduced sound can be normally heard at each seat is narrowed. Therefore, there is a concern that the seated person may not be able to normally hear the reproduced sound.

[0044] Furthermore, since the speaker array 9 is configured by arranging N speakers 2a to 2h in a row, it is difficult to reduce the size of the speaker array 9. Therefore, it is difficult to install the speaker array 9 at each of a plurality of seats close to each other in a train, an aircraft, a car, or the like.

[0045] Therefore, the present inventors have conducted intensive studies on a technology that can normally listen to reproduced sound in a reproduction area and can prevent the reproduced sound leaking to the outside of the reproduction area from being recognized, and have conceived of the various aspects of the present disclosure shown below.

[0046] (1) An audio device according to one embodiment of the present disclosure adjusts reproduced sound so that the reproduced sound reproduced by a speaker can be listened to in a given reproduction area, and comprises: a first generating unit that generates a background noise signal representing ambient sound around the microphone based on a reproduced signal output from a sound source of the reproduced sound, a detection sound signal representing detection sound detected by a microphone arranged near the speaker, and a first characteristic being a transfer characteristic of a sound signal from the speaker to the microphone; a second generating unit that generates a leakage sound signal representing the reproduced sound listened to at a representative point located outside the reproduction area based on the reproduced signal and a second characteristic being a transfer characteristic of a sound signal from the speaker to the representative point; and an adjusting unit that adjusts the level of the reproduced signal so that the level of the leakage sound signal is lower than the level of the background noise signal.

[0047] In this structure, a background noise signal representing the ambient sound around the microphone and a leakage sound signal representing the reproduced sound listened to at a representative point outside the reproduction area are generated, and the level of the reproduced signal is adjusted so that the level of the leakage sound signal is lower than the level of the background noise signal.

[0048] Thus, in this structure, instead of comparing the regenerated sound detected by the microphone with a larger level with the level of the background noise signal, the level of the leakage sound signal representing the regenerated sound listened at a representative point located outside the regeneration area is compared with the level of the background noise signal to adjust the level of the regenerated signal. Therefore, the level of the regenerated signal can be adjusted appropriately without excessively adjusting it. Thus, this structure can listen to the regenerated sound normally in the regeneration area. Moreover, this structure can also make the level of the regenerated sound listened at the representative point represented by the leakage sound signal smaller than the level of the ambient sound around the microphone represented by the background noise signal, thereby avoiding the recognition of the regenerated sound leaked to the outside of the regeneration area.

[0049] (2) In the audio device described in (1) above, the adjustment unit may calculate a difference level between the level of a target frequency component in the leakage signal, which is a frequency component whose level is greater than that of the background noise signal, and the level of a frequency component in the background noise signal corresponding to the target frequency component, so as to attenuate the level of the frequency component in the reproduced signal corresponding to the target frequency component by more than the difference level.

[0050] According to this configuration, it is possible to appropriately suppress only the frequency component of the ambient sound around the microphone, which has a higher level than that of the reproduced sound, from leaking outside the reproduction area.

[0051] (3) In the audio device described in (1) or (2) above, the first generating unit may perform the following processing: based on the reproduced sound signal and the first characteristic, generate a reproduced sound signal representing the reproduced sound listened to at the setting position of the microphone, and generate a signal obtained by subtracting the reproduced sound signal from the detected sound signal as the background noise signal; and the second generating unit may perform the following processing: based on the reproduced sound signal and an approximate characteristic that approximates the difference characteristic between the first characteristic and the second characteristic, generate the leakage sound signal.

[0052] According to this structure, a leakage sound signal is generated based on the reproduced sound signal generated by the first generating unit and the approximate characteristic that approximates the difference characteristic between the first characteristic and the second characteristic. Therefore, compared with the case where the leakage sound signal is generated based on the reproduced signal and the second characteristic, this structure can reduce the size of the structure and the amount of calculation required for generating the leakage sound signal.

[0053] (4) In the audio device described in (3) above, the approximate characteristic may indicate that the levels of each of a plurality of frequency components in the audio signal are constant.

[0054] According to this configuration, since the approximation characteristic shows that the levels of each of the plurality of frequency components in the audio signal are constant, a leakage sound signal can be easily generated simply by uniformly changing the levels of all frequency components of the reproduced sound signal by a constant amount.

[0055] (5) In the audio device described in (3) above, the approximate characteristic may also show that the level of the frequency component in the sound signal that is lower than a given reference frequency component is a constant first level, and the level of the frequency component in the sound signal that is higher than the reference frequency component is a constant second level that is different from the first level.

[0056] In this structure, the approximate characteristics show that the level of the frequency component lower than the reference frequency component in the sound signal and the level of the frequency component higher than the reference frequency component are different constant levels. Therefore, according to this structure, it is possible to easily generate a leakage sound signal by simply changing the level of the frequency component lower than the reference frequency component in the reproduced sound signal by a constant amount and changing the level of the frequency component higher than the reference frequency component in the reproduced sound signal by a constant amount.

[0057] (6) An audio device according to another aspect of the present disclosure adjusts a first reproduced sound and a second reproduced sound so that the first reproduced sound reproduced by a first speaker is listened to in a given first reproduction area, and the second reproduced sound reproduced by a second speaker is listened to in a given second reproduction area, wherein the first speaker is provided at a first seat, and the second speaker is provided at a second seat close to the first seat, and the audio device comprises a first generating unit, a second generating unit, and an adjusting unit, wherein the first generating unit performs the following processing: generating a first background noise signal representing ambient sound around the first microphone based on a first reproduced signal output from a sound source of the first reproduced sound, a first detection sound signal representing a detection sound detected by a first microphone provided close to the first speaker, and a first transfer characteristic being a transfer characteristic of a sound signal from the first speaker to the first microphone, and generating a first background noise signal representing ambient sound around the first microphone based on a second reproduced signal output from a sound source of the second reproduced sound, a second detection sound signal representing a detection sound detected by the second microphone provided close to the second speaker, and a first transfer characteristic being a transfer characteristic of a sound signal from the first speaker to the first microphone The second generating unit generates a second background noise signal representing the ambient sound around the second microphone based on a second transfer characteristic which is a transfer characteristic of the sound signal from the second speaker to the second microphone, the second generating unit performs the following processing: based on the first reproduced signal and a third transfer characteristic which is a transfer characteristic of the sound signal from the first speaker to a first representative point located in the second reproduced area, generates a first leakage sound signal representing the first reproduced sound listened to at the first representative point, based on the second reproduced signal and a fourth transfer characteristic which is a transfer characteristic of the sound signal from the second speaker to a second representative point located in the first reproduced area, generates a second leakage sound signal representing the second reproduced sound listened to at the second representative point, and the adjusting unit performs the following processing: adjusting the level of the first reproduced signal so that the level of the first leakage sound signal is lower than the level of the first background noise signal, and adjusting the level of the second reproduced signal so that the level of the second leakage sound signal is lower than the level of the second background noise signal.

[0058] In this structure, a first background noise signal representing the ambient sound around the first microphone and a first leakage sound signal representing the first reproduced sound listened to at a first representative point located in the second reproduction area are generated, and the level of the first reproduced signal is adjusted so that the level of the first leakage sound signal is smaller than the level of the first background noise signal.

[0059] Thus, in the present structure, instead of comparing the first reproduced sound having a larger level detected by the first microphone with the level of the first background noise signal, the level of the first leakage sound signal representing the first reproduced sound listened to at a representative point located in the second reproduction area is compared with the level of the first background noise signal to adjust the level of the first reproduced signal. Therefore, the level of the first reproduced signal can be adjusted appropriately without excessively adjusting it. Thus, the present structure can normally listen to the first reproduced sound reproduced by the first speaker set at the first seat in the first reproduction area. Moreover, the present structure can also make the level of the first reproduced sound listened to at a representative point in the second reproduction area represented by the first leakage sound signal lower than the level of the ambient sound around the first microphone represented by the first background noise signal, thereby avoiding the first reproduced sound reproduced at the first seat from being recognized in the second reproduction area.

[0060] Similarly, this configuration allows the second reproduced sound reproduced by the second speaker installed at the second seat to be normally heard in the second reproduction area. In addition, this configuration can also prevent the second reproduced sound reproduced at the second seat from being recognized in the first reproduction area.

[0061] (7) In the audio device described in (6) above, the adjustment unit may perform the following processing: calculating a first difference level as a difference between a level of a first frequency component, which is a frequency component having a level greater than that of the first background noise signal in the first leakage sound signal, and a level of a frequency component corresponding to the first frequency component in the first background noise signal, so that the level of the frequency component corresponding to the first frequency component in the first regenerated signal is attenuated by more than the first difference level; calculating a second difference level as a difference between a level of a second frequency component, which is a frequency component having a level greater than that of the second background noise signal in the second leakage sound signal, and a level of a frequency component corresponding to the second frequency component in the second background noise signal, so that the level of the frequency component corresponding to the second frequency component in the second regenerated signal is attenuated by more than the second difference level.

[0062] According to this structure, only the frequency components of the first reproduced sound leaking into the second reproduced area whose level is higher than the ambient sound around the first microphone can be appropriately suppressed. Similarly, only the frequency components of the second reproduced sound leaking into the first reproduced area whose level is higher than the ambient sound around the second microphone can be appropriately suppressed.

[0063] (8) In the audio device described in (6) or (7) above, the first generating unit may perform the following processing: based on the first reproduced signal and the first transfer characteristic, generating a first reproduced sound signal representing the first reproduced sound listened to at the installation position of the first microphone, generating a signal obtained by subtracting the first reproduced sound signal from the first detection sound signal as the first background noise signal, and based on the second reproduced signal and the second transfer characteristic, generating a second reproduced sound signal representing the first reproduced sound listened to at the installation position of the second microphone. The second generation unit generates a second regenerated sound signal of the generated sound, and generates a signal obtained by subtracting the second regenerated sound signal from the second detected sound signal, as the second background noise signal. The second generation unit performs the following processing: generates the first leakage sound signal based on the first regenerated sound signal and the first approximate characteristic that approximates the difference characteristic between the first transfer characteristic and the third transfer characteristic, and generates the second leakage sound signal based on the second regenerated sound signal and the second approximate characteristic that approximates the difference characteristic between the second transfer characteristic and the fourth transfer characteristic.

[0064] According to this structure, the first leakage sound signal is generated based on the first reproduced sound signal generated by the first generating unit and the first approximate characteristic that approximates the difference characteristic between the first transfer characteristic and the third transfer characteristic. Therefore, compared with the case where the first leakage sound signal is generated based on the first reproduced signal and the third transfer characteristic, the present structure can reduce the size of the structure and the amount of calculation required for generating the first leakage sound signal. Similarly, according to this structure, compared with the case where the second leakage sound signal is generated based on the second reproduced signal and the fourth transfer characteristic, the size of the structure and the amount of calculation required for generating the second leakage sound signal can be reduced.

[0065] (9) In the audio device described in (8) above, the first approximate characteristic and the second approximate characteristic may indicate that the levels of each of a plurality of frequency components in the audio signal are constant.

[0066] In this structure, the first approximate characteristic and the second approximate characteristic show that the levels of the plurality of frequency components in the sound signal are constant. Therefore, according to this structure, the first leakage sound signal can be easily generated by simply changing the levels of all the frequency components of the first reproduced sound signal by a constant amount. Similarly, according to this structure, the second leakage sound signal can be easily generated by simply changing the levels of all the frequency components of the second reproduced sound signal by a constant amount.

[0067] (10) In the audio device described in (8) above, the first approximate characteristic and the second approximate characteristic may indicate that the level of the frequency component in the sound signal that is lower than a given reference frequency component is a constant first level, and the level of the frequency component in the sound signal that is higher than the reference frequency component is a constant second level that is different from the first level.

[0068] In the present structure, the first approximate characteristic and the second approximate characteristic show that the levels of the frequency components lower than the reference frequency component and the levels of the frequency components higher than the reference frequency component in the sound signal are different constant levels. Therefore, according to the present structure, the first leakage sound signal can be easily generated only by uniformly changing the levels of the frequency components lower than the reference frequency component in the first reproduced sound signal by a constant amount and uniformly changing the levels of the frequency components higher than the reference frequency component in the first reproduced sound signal by a constant amount. Similarly, according to the present structure, the second leakage sound signal can be easily generated only by uniformly changing the levels of the frequency components lower than the reference frequency component in the second reproduced sound signal by a constant amount and uniformly changing the levels of the frequency components higher than the reference frequency component in the second reproduced sound signal by a constant amount.

[0069] (11) In the audio device described in (6) above, the first representative point may be a position where the second microphone is installed, and the second representative point may be a position where the first microphone is installed.

[0070] According to this structure, since the first representative point located in the second reproduction area is the position where the second microphone is set, the third transfer characteristic which is the transfer characteristic of the sound signal from the first speaker to the first representative point can be derived using the second detection sound signal representing the detection sound detected by the second microphone.

[0071] Therefore, this configuration can reduce the cost and effort required to derive the third transfer characteristic, compared to a case where a microphone other than the second microphone is provided in the second reproduction area to derive the transfer characteristic of the sound signal from the first speaker to the installation position of the microphone as the third transfer characteristic. Similarly, according to this configuration, compared to a case where a microphone other than the first microphone is provided in the first reproduction area to derive the transfer characteristic of the sound signal from the second speaker to the installation position of the microphone as the fourth transfer characteristic, the cost and effort required to derive the fourth transfer characteristic can be reduced.

[0072] (12) In the audio device described in (1) above, the speaker may include a first speaker and a second speaker installed at the same seat, the reproduction area may include: a common reproduction area for listening to a first reproduced sound reproduced by the first speaker and a second reproduced sound reproduced by the second speaker, the representative point may include a first representative point and a second representative point located outside the common reproduction area, the microphone may include: a first microphone installed close to the first speaker; and a second microphone installed close to the second speaker, the first characteristic may include a first first characteristic which is a transfer characteristic of a sound signal from the first speaker to the first microphone, and a second first characteristic which is a transfer characteristic of a sound signal from the second speaker to the second microphone, the second characteristic may include a first second characteristic which is a transfer characteristic of a sound signal from the first speaker to the first representative point, and a second second characteristic which is a transfer characteristic of a sound signal from the second speaker to the second representative point, and the first generating unit may perform the following processing: based on the first characteristic from A first background noise signal representing ambient sound around the first microphone is generated based on a first reproduced signal output from the sound source of the first reproduced sound, a first detection sound signal representing the detection sound detected by the first microphone, and the first first characteristic; a second background noise signal representing ambient sound around the second microphone is generated based on a second reproduced signal output from the sound source of the second reproduced sound, a second detection sound signal representing the detection sound detected by the second microphone, and the second first characteristic; the second generating unit performs the following processing: based on the first reproduced signal and the first second characteristic, a first leakage sound signal representing the first reproduced sound listened to at the first representative point is generated; based on the second reproduced signal and the second second characteristic, a second leakage sound signal representing the second reproduced sound listened to at the second representative point is generated; the adjusting unit adjusts the levels of the first reproduced signal and the second reproduced signal so that the level of the first leakage sound signal is lower than the level of the first background noise signal, and the level of the second leakage sound signal is lower than the level of the second background noise signal.

[0073] In this structure, a first background noise signal representing the ambient sound around the first microphone and a first leakage sound signal representing the first reproduced sound listened to at a first representative point outside the common reproduction area are generated, and a second background noise signal representing the ambient sound around the second microphone and a second leakage sound signal representing the second reproduced sound listened to at a second representative point outside the common reproduction area are generated. In addition, the levels of the first reproduced signal and the second reproduced signal are adjusted so that the level of the first leakage sound signal is lower than the level of the first background noise signal, and the level of the second leakage sound signal is lower than the level of the second background noise signal.

[0074] Thus, in the present structure, instead of comparing the first regenerated sound detected by the first microphone with a larger level with the level of the first background noise signal, the level of the first leakage sound signal representing the first regenerated sound listened to at the first representative point is compared with the level of the first background noise signal, and instead of comparing the second regenerated sound detected by the second microphone with a larger level with the level of the second background noise signal, the level of the second leakage sound signal representing the second regenerated sound listened to at the second representative point is compared with the level of the second background noise signal to adjust the levels of the first regenerated signal and the second regenerated signal. Therefore, the present structure can adjust the levels of the first regenerated signal and the second regenerated signal appropriately without excessively adjusting them. Thus, the present structure can normally listen to the first regenerated sound and the second regenerated sound in the common regeneration area for listening to the first regenerated sound and the second regenerated sound.

[0075] Moreover, the present structure can also make the level of the first reproduced sound listened at the first representative point represented by the first leakage sound signal lower than the level of the ambient sound around the first microphone represented by the first background noise signal, and make the level of the second reproduced sound listened at the second representative point represented by the second leakage sound signal lower than the level of the ambient sound around the second microphone represented by the second background noise signal, thereby avoiding the first reproduced sound and the second reproduced sound from being recognized outside the common reproduction area.

[0076] (13) In the audio device described in (12) above, the adjustment unit may perform the following processing: determining a first frequency component in the first leakage sound signal as a frequency component having a level greater than that of the first background noise signal, and determining a second frequency component in the second leakage sound signal as a frequency component having a level greater than that of the second background noise signal, so that the level of the frequency component corresponding to the first frequency component or the second frequency component in each of the first regenerated signal and the second regenerated signal, i.e., the third frequency component, is attenuated by more than the larger of the difference between the level of the third frequency component in the first leakage sound signal and the level of the third frequency component in the first background noise signal and the difference between the level of the third frequency component in the second leakage sound signal and the level of the third frequency component in the second background noise signal.

[0077] According to the present structure, the levels of the third frequency component in each of the first reproduced sound and the second reproduced sound leaking to the outside of the common reproduction area can be appropriately suppressed by using the larger difference between the level of the third frequency component in the first leakage sound signal and the level of the third frequency component in the first background noise signal, and the level of the third frequency component in the second leakage sound signal and the level of the third frequency component in the second background noise signal.

[0078] (14) Another aspect of the present disclosure relates to a reproduction method in an audio device that adjusts reproduced sound so that the reproduced sound reproduced by a speaker is listened to in a given reproduction area. In the reproduction method, a background noise signal representing ambient sound around the microphone is generated based on a reproduction signal output from a sound source of the reproduced sound, a detection sound signal representing detection sound detected by a microphone arranged near the speaker, and a first characteristic being a transfer characteristic of a sound signal from the speaker to the microphone. A leakage sound signal representing the reproduced sound listened to at a representative point outside the reproduction area is generated based on the reproduction signal and a second characteristic being a transfer characteristic of a sound signal from the speaker to the representative point. The level of the reproduction signal is adjusted so that the level of the leakage sound signal is smaller than the level of the background noise signal.

[0079] According to this configuration, the same operational effects as those of the acoustic device described in (1) above can be obtained.

[0080] (15) Another aspect of the present disclosure relates to a program that causes a computer of an audio device that adjusts reproduced sound so that the reproduced sound reproduced by a speaker is listened to in a given reproduction area to execute processing, the program causing the computer to execute the following processing: generating a background noise signal representing ambient sound around the microphone based on a reproduced signal output from a sound source of the reproduced sound, a detection sound signal representing detection sound detected by a microphone installed near the speaker, and a first characteristic being a transfer characteristic of a sound signal from the speaker to the microphone; generating a leakage sound signal representing the reproduced sound listened to at a representative point based on the reproduced signal and a second characteristic being a transfer characteristic of a sound signal from the speaker to a representative point outside the reproduction area; and adjusting the level of the reproduced signal so that the level of the leakage sound signal is lower than the level of the background noise signal.

[0081] According to this configuration, the same operational effects as those of the acoustic device described in (1) above can be obtained.

[0082] (16) Another aspect of the present disclosure relates to a reproduction method in an audio device, wherein the audio device adjusts a first reproduced sound and a second reproduced sound so that the first reproduced sound reproduced by a first speaker is listened to in a given first reproduction area, and the second reproduced sound reproduced by a second speaker is listened to in a given second reproduction area, wherein the first speaker is provided at a first seat, and the second speaker is provided at a second seat close to the first seat, wherein the reproduction method generates a first background noise signal representing ambient sound around the first microphone based on a first reproduced signal output from a sound source of the first reproduced sound, a first detection sound signal representing a detection sound detected by a first microphone provided close to the first speaker, and a first transfer characteristic being a transfer characteristic of a sound signal from the first speaker to the first microphone, and generates a first background noise signal representing ambient sound around the first microphone based on a second reproduced signal output from a sound source of the second reproduced sound, a second detection sound signal representing a detection sound detected by the second microphone provided close to the second speaker. A second background noise signal representing the ambient sound around the second microphone is generated based on the sound measurement signal and the second transfer characteristic which is the transfer characteristic of the sound signal from the second speaker to the second microphone; a first leakage sound signal representing the first reproduced sound listened to at the first representative point is generated based on the first reproduced signal and the third transfer characteristic which is the transfer characteristic of the sound signal from the first speaker to the first representative point located in the second reproduced area; a second leakage sound signal representing the second reproduced sound listened to at the second representative point is generated based on the second reproduced signal and the fourth transfer characteristic which is the transfer characteristic of the sound signal from the second speaker to the second representative point located in the first reproduced area; the level of the first reproduced signal is adjusted so that the level of the first leakage sound signal is smaller than the level of the first background noise signal; and the level of the second reproduced signal is adjusted so that the level of the second leakage sound signal is smaller than the level of the second background noise signal.

[0083] According to this configuration, the same operational effects as those of the acoustic device described in (6) above can be obtained.

[0084] (17) A program according to another aspect of the present disclosure causes a computer of an audio device to execute processing, wherein the audio device adjusts a first reproduced sound and a second reproduced sound so that the first reproduced sound reproduced by a first speaker is listened to in a given first reproduction area, and the second reproduced sound reproduced by a second speaker is listened to in a given second reproduction area, wherein the first speaker is provided at a first seat, and the second speaker is provided at a second seat close to the first seat, and the program causes the computer to execute the following processing: generating a first background noise signal representing ambient sound around the first microphone based on a first reproduced signal output from a sound source of the first reproduced sound, a first detection sound signal representing a detection sound detected by a first microphone provided close to the first speaker, and a first transfer characteristic being a transfer characteristic of a sound signal from the first speaker to the first microphone, and generating a first background noise signal representing ambient sound around the first microphone based on a second reproduced signal output from a sound source of the second reproduced sound, a first detection sound signal representing a detection sound detected by the second microphone provided close to the second speaker, and a first transfer characteristic being a transfer characteristic of a sound signal from the first speaker to the first microphone. a second background noise signal representing the ambient sound around the second microphone based on the second detection sound signal and the second transfer characteristic being the transfer characteristic of the sound signal from the second speaker to the second microphone; a first leakage sound signal representing the first reproduced sound listened to at the first representative point based on the first reproduced signal and the third transfer characteristic being the transfer characteristic of the sound signal from the first speaker to the first representative point within the second reproduced area; a second leakage sound signal representing the second reproduced sound listened to at the second representative point based on the second reproduced signal and the fourth transfer characteristic being the transfer characteristic of the sound signal from the second speaker to the second representative point within the first reproduced area; the level of the first reproduced signal is adjusted so that the level of the first leakage sound signal is smaller than the level of the first background noise signal; and the level of the second reproduced signal is adjusted so that the level of the second leakage sound signal is smaller than the level of the second background noise signal.

[0085] According to this configuration, the same operational effects as those of the acoustic device described in (6) above can be obtained.

[0086] The present disclosure can also be realized as a system operated by such a program. In addition, such a computer program can of course be distributed via a non-transitory recording medium such as a CD-ROM that can be read by a computer or a communication network such as the Internet.

[0087] In addition, the embodiments described below all represent a specific example of the present disclosure. The structural elements, the configuration positions of the structural elements, the connection methods, and the order of actions shown in the following embodiments are examples and are not intended to limit the present disclosure. In addition, for the structural elements in the following embodiments that are not recorded in the independent technical solutions representing the highest concept, they are described as arbitrary structural elements. In addition, in all embodiments, the various contents can also be combined.

[0088] (First embodiment)

[0089] Hereinafter, the configuration of acoustic system 1 according to the first embodiment will be described. Figure 1A It is a plan view showing an example of the structure of the acoustic system 1 according to the first embodiment. Figure 1B 1 is a front view showing an example of the structure of the acoustic system 1 according to the first embodiment. Figure 1A As shown, the audio system 1 includes a speaker 2 , a microphone 3 , a sound source 10 , and an audio device 11 .

[0090] In the audio system 1, an audio signal representing music and / or voice output from a sound source 10 such as a CD player is processed by an audio device 11 and then reproduced by a speaker 2. The reproduced sound reproduced by the speaker 2 is detected by a microphone 3 provided near the speaker 2. A detection sound signal representing the detection sound detected by the microphone 3 is input to the audio device 11.

[0091] The sound system 1 listens to the reproduced sound reproduced by the speaker 2 in the reproduction area 100 provided at a position close to the speaker 2 just in front of the speaker 2. On the other hand, the sound system 1 prevents the reproduced sound from being recognized in the non-reproduction area 200 located outside the reproduction area 100. Therefore, the sound device 11 adjusts the level of the audio signal output from the sound source 10 using the detection sound signal detected by the microphone 3.

[0092] However, in reality, since the reproduced sound also leaks into the non-reproduced area 200, it is difficult to make the reproduced sound level "0" in the non-reproduced area 200. However, if the level of the reproduced sound leaking into the non-reproduced area 200 (hereinafter referred to as leakage sound) is lower than the level of the ambient sound around the non-reproduced area 200 (hereinafter referred to as background noise), the leakage sound is masked by the background noise and cannot be heard.

[0093] Figure 2 as well as Figure 3 2 is a diagram showing an example of the frequency characteristics of the reproduced sound and the background noise in the non-reproduced area 200. Figure 2 as well as Figure 3In FIG. 2 , the horizontal axis represents the frequency components of the reproduced sound and the background noise in the non-reproduced area 200, and the vertical axis represents the level of each frequency component of the reproduced sound and the background noise. Figure 2 As shown, when the level of the reproduced sound of the frequency components above the frequency f1 is greater than the level of the background noise, the reproduced sound of the frequency components above the frequency f1 is recognized by a person located at the representative point 201 representing the non-reproduction area 200. On the other hand, the reproduced sound of the frequency components below the frequency f1 is masked by the background noise and therefore is not recognized by a person located at the representative point 201 representing the non-reproduction area 200.

[0094] In addition, general background noise has a characteristic that the level decreases as the frequency increases. For example, not only the noise of transportation vehicles such as trains, aircraft and cars, but also the noise of factories and noise in offices have this characteristic.

[0095] For this reason, Figure 3 As shown, audio device 11 performs signal processing to reduce the level of frequency components above frequency f1 in the audio signal. As a result, the level of the reproduced sound at representative point 201 does not exceed the level of background noise, and the reproduced sound is not recognized by a person at representative point 201.

[0096] Figure 4 as well as Figure 5 1 is a diagram showing an example of frequency characteristics of reproduced sound and background noise in the reproduction area 100. Figure 4 as well as Figure 5 In FIG. 1 , the horizontal axis represents the frequency components of the reproduced sound and background noise in the reproduction area 100, and the vertical axis represents the level of each frequency component of the reproduced sound and background noise. If the above signal processing is performed in the audio device 11, the level of the frequency components above the frequency f1 of the reproduced sound heard by the person in the reproduction area 100 is also reduced. However, since the reproduction area 100 is closer to the speaker 2 than the representative point 201, before the above signal processing is performed, for example, Figure 4 As shown in FIG. 1 , the level of the reproduced sound is sufficiently greater than the level of the background noise. Figure 5 As shown, after the above signal processing is performed, the reproduced sound will not be masked by the background noise and can be recognized by people located in the reproduction area 100.

[0097] use Figure 6 The above-mentioned signal processing performed in the audio device 11 will be described in more detail. Figure 6 1 is a diagram showing an example of a detailed configuration of the acoustic system 1 according to the first embodiment. Figure 6As shown, audio device 11 is configured by a computer including a CPU (Central Processing Unit) such as a DSP (Digital Signal Processor) or an MPU (Micro-Processing Unit), a memory, and an integrated circuit such as an FPGA (Field Programmable Gate Array).

[0098] The audio device 11 functions as the first generation unit 21, the second generation unit 22, and the adjustment unit 20 by the CPU executing the control program (program) stored in the memory. The first generation unit 21 includes a transfer characteristic correction unit 131 and a subtraction unit 14, and the second generation unit 22 includes a transfer characteristic correction unit 132. The adjustment unit 20 includes two frequency analysis units 151 and 152, a comparison unit 16, and a correction unit 12. In addition, each of the first generation unit 21, the second generation unit 22, and the adjustment unit 20 may be configured by a dedicated hardware circuit.

[0099] The audio signal S (reproduction signal) adjusted to a level corresponding to the volume set by the listener and outputted in the sound source 10 is inputted to the adjustment unit 20. In the adjustment unit 20, the correction unit 12 adjusts the inputted audio signal S to a level corresponding to a given initial value (for example, 0 dB), and causes the speaker 2 to reproduce the adjusted audio signal S. The microphone 3 detects a sound in which the reproduced sound reproduced by the speaker 2 and the background noise N around the microphone 3 are mixed, and outputs a detection sound signal representing the detected detection sound to the subtraction unit 14.

[0100] The audio signal S output from the sound source 10 is also input to the first generating unit 21. The first generating unit 21 generates a background noise signal representing the ambient sound around the microphone 3 based on the input audio signal S, the detection sound signal representing the detection sound detected by the microphone 3, and the transfer characteristic (first characteristic) of the sound signal from the speaker 2 to the microphone 3.

[0101] Specifically, in the first generating unit 21, the transfer characteristic modifying unit 131 performs convolution processing on the input audio signal S using the coefficient "C11", thereby generating the signal after the convolution processing as a reproduced sound signal representing the reproduced sound heard at the installation position of the microphone 3. The transfer characteristic modifying unit 131 outputs the generated reproduced sound signal to the subtracting unit 14.

[0102] Here, the coefficient "C11" is a coefficient that approximates the transfer characteristic of the sound signal from the speaker 2 to the microphone 3. The coefficient "C11" is predetermined based on the detection sound signal representing the detection sound detected by the microphone 3 when the speaker 2 reproduces the sound signal for the experiment, for example. Hereinafter, the coefficient "C11" may be described as the transfer characteristic C11 from the speaker 2 to the microphone 3.

[0103] The subtracting unit 14 generates a signal obtained by subtracting the reproduced sound signal generated by the transfer characteristic correction unit 131 from the detected sound signal indicating the detected sound detected by the microphone 3 , as a background noise signal indicating the background noise around the microphone 3 .

[0104] Specifically, the detection sound signal representing the detection sound detected by the microphone 3 can be expressed as "C11·S+N", and the reproduction sound signal generated by the transfer characteristic correction unit 131 can be expressed as "C11·S". Here, "S" represents the audio signal S. "N" is a sound signal representing the background noise N around the microphone 3. The subtraction unit 14 generates a sound signal "N (=C11·S+N-C11·S)" obtained by subtracting the reproduction sound signal "C11·S" from the detection sound signal "C11·S+N", as a background noise signal representing the background noise around the microphone 3.

[0105] The audio signal S output from the sound source 10 is also input to the second generation unit 22. The second generation unit 22 generates a leakage sound signal representing the reproduced sound heard at the representative point 201 based on the input audio signal S and the transfer characteristic (second characteristic) of the sound signal from the speaker 2 to the representative point 201 of the non-reproduction area 200.

[0106] Specifically, in the second generation unit 22 , the transfer characteristic correction unit 132 performs convolution processing on the input audio signal S using the coefficient “C13”, thereby generating a sound signal “C13·S” after the convolution processing as a leakage signal representing the reproduced sound heard at the representative point 201 of the non-reproduction area 200 .

[0107] Here, the coefficient "C13" is a coefficient that approximates the transfer characteristic of the sound signal from the speaker 2 to the representative point 201 of the non-reproduction area 200. The coefficient "C13" is predetermined based on the detection sound signal representing the detection sound detected by the microphone set at the representative point 201 of the non-reproduction area 200, for example, when the speaker 2 reproduces the sound signal for the experiment. In the following, the coefficient "C13" may be described as the transfer characteristic C13 from the speaker 2 to the representative point 201.

[0108] The representative point 201 of the non-reproduction area 200 may be any position outside the reproduction area 100, such as the position of the microphone 3 installed near the speaker 2. When the representative point 201 is the position of the microphone 3, the coefficient "C13" can be determined using the microphone 3 without taking the trouble of moving the installation position of the microphone 3 or installing a microphone other than the microphone 3 at the representative point 201.

[0109] The adjuster 20 adjusts the level of the audio signal S input from the sound source 10 so that the level of the leakage sound signal generated by the second generator 22 is lower than the level of the background noise signal generated by the first generator 21. The adjuster 20 causes the speaker 2 to reproduce the adjusted audio signal S.

[0110] Specifically, in the adjustment unit 20, the frequency analysis unit 151 calculates the levels of the multiple frequency components in the background noise signal generated by the first generation unit 21 by performing a given frequency analysis process such as a fast Fourier transform (FFT). The frequency analysis unit 152, like the frequency analysis unit 151, calculates the levels of the multiple frequency components in the leakage sound signal generated by the second generation unit 22 by performing a given frequency analysis process such as a fast Fourier transform (FFT).

[0111] The comparison unit 16 compares the levels of each frequency component of the background noise signal calculated by the frequency analysis unit 151 and the levels of each frequency component of the leakage signal calculated by the frequency analysis unit 152, and outputs the magnitude relationship between the levels of each frequency component of the background noise signal and the levels of each frequency component of the leakage signal and the difference as the comparison result to the correction unit 12.

[0112] The correction unit 12 adjusts the level of the audio signal S input from the sound source 10 so that the level of the leakage sound signal is lower than the level of the background noise signal based on the comparison result input from the comparison unit 16. The correction unit 12 causes the speaker 2 to reproduce the adjusted audio signal S.

[0113] Specifically, the correction unit 12 attenuates the level of the frequency component corresponding to the object frequency component in the audio signal S by more than the difference between the level of the frequency component of the leakage signal whose level is greater than that of the background noise signal (hereinafter referred to as the object frequency component) and the level of the frequency component corresponding to the object frequency component in the background noise signal.

[0114] For example, the correction unit 12 attenuates the level of the frequency component corresponding to the target frequency component in the audio signal S by a level greater than a given error level than the difference between the level of the target frequency component in the leakage sound signal and the level of the frequency component corresponding to the target frequency component in the background noise signal. The frequency component corresponding to the target frequency component in the sound signal refers to a frequency component having the same frequency as the target frequency component among a plurality of frequency components included in the sound signal.

[0115] However, this is not limited to this. The correction unit 12 may not use the above-mentioned error level, but make the level of the frequency component corresponding to the object frequency component in the audio signal S attenuate the difference between the level of the object frequency component in the leakage signal and the level of the frequency component corresponding to the object frequency component in the background noise signal.

[0116] Next, the flow of the above-mentioned signal processing performed in audio device 11 will be described. Figure 7 1 is a flowchart showing an example of signal processing performed in the audio device 11. Figure 7 As shown, when the sound source 10 starts outputting the audio signal S adjusted to a level according to the volume set by the listener, the audio signal S is input to the correction unit 12 , the first generation unit 21 , and the second generation unit 22 (step ST1 ).

[0117] The correction unit 12 causes the speaker 2 to reproduce the audio signal S input in step ST1. In addition, the correction unit 12 causes the speaker 2 to reproduce the audio signal S whose level is adjusted in step S6 described later (step ST2). The microphone 3 detects a sound in which the reproduced sound reproduced by the speaker 2 and the background noise around the microphone 3 are mixed, and outputs a detection sound signal indicating the detected detection sound to the subtraction unit 14 (step ST3).

[0118] The first generator 21 generates a background noise signal representing ambient sound around the microphone 3 based on the input audio signal S, the detection sound signal representing the detection sound detected by the microphone 3 , and the transfer characteristic C11 of the sound signal from the speaker 2 to the microphone 3 (step ST4 ).

[0119] The second generation unit 22 generates a leakage sound signal representing the reproduced sound heard at the representative point 201 based on the input audio signal S and the transfer characteristic C13 of the sound signal from the speaker 2 to the representative point 201 of the non-reproduction area 200 (step ST5 ).

[0120] The adjustment unit 20 adjusts the level of the audio signal S input from the sound source 10 so that the level of the leakage sound signal generated in step ST5 is lower than the level of the background noise signal generated in step ST4 (step ST6 ).

[0121] If the output of the audio signal S by the sound source 10 has not yet been completed (No in step ST7 ), the processing after step ST2 is repeated. On the other hand, if the output of the audio signal S by the sound source 10 has been completed (Yes in step ST7 ), the audio device 11 ends the signal processing.

[0122] Next, the effects obtained by the configuration of the first embodiment will be described. Figure 8 1 is a diagram showing an example of a transfer characteristic C11 from the speaker 2 to the microphone 3 and a transfer characteristic C13 from the speaker 2 to a representative point 201 of the non-reproduction area 200 .

[0123] like Figure 6 As shown in FIG. 1 , the distance from the speaker 2 to the representative point 201 of the non-reproduction area 200 is longer than the distance from the speaker 2 to the microphone 3. Therefore, due to the influence of distance attenuation, the level of the reproduced sound at the representative point 201 is lower than the level of the reproduced sound at the installation position of the microphone 3. Therefore, for example, Figure 8 As shown, the level of the transfer characteristic C13 from the speaker 2 to the representative point 201 is lower than the level of the transfer characteristic C11 from the speaker 2 to the microphone 3 .

[0124] In the structure of the first embodiment, a background noise signal representing the ambient sound around the microphone 3 and a leakage sound signal representing the reproduced sound listened to at the representative point 201 of the non-reproduction area 200 are generated, and the level of the audio signal S is adjusted so that the level of the leakage sound signal is lower than the level of the background noise signal.

[0125] Thus, in this structure, instead of comparing the reproduced sound detected by the microphone 3 with the background noise signal, the leakage sound signal representing the reproduced sound listened at the representative point 201 is compared with the background noise signal to adjust the audio signal S. Therefore, the level of the audio signal S can be adjusted appropriately without excessively adjusting it. Thus, this structure enables the listener located in the reproduction area 100 to listen to the reproduced sound normally. Moreover, this structure can also make the level of the reproduced sound listened in the non-reproduction area 200 represented by the leakage sound signal lower than the level of the ambient sound around the microphone 3 represented by the background noise signal, thereby avoiding the reproduction sound from being recognized in the non-reproduction area 200.

[0126] (Modification of the first embodiment)

[0127] The structure of the first embodiment may be modified as follows. Fig.9A as well as Fig. 9B 1 is a diagram showing an example of a difference characteristic C1311 between the two transfer characteristics C13 and C11 and an example of an approximate characteristic CA13. Fig.9A as well as Fig. 9B As shown, by approximating the difference characteristic C1311 between the transfer characteristic C11 and the transfer characteristic C13, it is possible to derive Fig.9A The dash-dot line and Fig. 9B Therefore, the second generation unit 22 may generate the sound leakage signal using the approximate characteristic CA13.

[0128] also, Fig.9A The approximate characteristic CA13 indicated by the single-dot chain line shows the following situation: the level of the frequency component below 1KHz in the sound signal is constant at -5dB, the level of the frequency component above 1KHz and below 2KHz increases linearly from -5dB to 0dB, and the level of the frequency component above 2KHz is constant at 0dB. That is, the approximate characteristic CA13 approximates the difference characteristic C1311 between the transfer characteristic C11 and the transfer characteristic C13 to be the same as the frequency characteristic of the low-frequency shelf filter. Fig. 9B The approximate characteristic CA13 indicated by the dotted line portion shows that the level of each frequency component in the audio signal is constant at -2 dB.

[0129] However, the approximate characteristic CA13 is not limited to Fig.9A as well as Fig. 9B The example shown may also show a situation where the level of frequency components in the sound signal lower than a reference frequency such as 1 kHz is constant at -5 dB, and the level of frequency components higher than the reference frequency of 1 kHz is constant at 0 dB.

[0130] Fig.10 1 is a diagram showing an example of a configuration of an audio system 1A according to a modification of the first embodiment. Fig.10 As shown, an audio system 1A according to this modification includes an audio device 11A which replaces the first generation unit 21 and the second generation unit 22 ( Figure 6 ) and functions as the first generation unit 21A and the second generation unit 22A. The first generation unit 21A replaces the transfer characteristic correction unit 131 ( Figure 6 ) and includes a transfer characteristic correction unit 131A. The second generation unit 22A replaces the transfer characteristic correction unit 132 ( Figure 6 ) and includes a transfer characteristic correction unit 132A.

[0131] In the first generation unit 21A, the transfer characteristic modification unit 131A outputs the generated reproduced sound signal not only to the subtraction unit 14 but also to the second generation unit 22A. In the second generation unit 22A, the transfer characteristic modification unit 132A generates a leakage sound signal using the reproduced sound signal and the approximate characteristic CA13 input from the first generation unit 21A instead of the audio signal S and the transfer characteristic C13 output from the sound source 10.

[0132] That is, the transfer characteristic modification unit 132A performs convolution processing on the reproduced sound signal "C11·S" generated by the transfer characteristic modification unit 131A using the approximate characteristic CA13 that approximates the difference characteristic C1311 between the transfer characteristic C13 and the transfer characteristic C11. As a result, the transfer characteristic modification unit 132 outputs a signal having the same Figure 6 The leakage signal having characteristics close to the leakage signal "C13·S" generated by the transfer characteristic correction unit 132A can be obtained. Figure 6 The same effects as those obtained by the configuration of the acoustic system 1 shown in FIG.

[0133] In addition, in the transfer characteristic correction unit 132A, when using Fig.9A When generating a leakage sound signal by using the approximate characteristic CA13 shown in FIG. 1 , the leakage sound signal can be easily generated by uniformly attenuating the level of the frequency components below 1 kHz in the reproduced sound signal by 5 dB and linearly attenuating the level of the frequency components above 1 kHz and below 2 kHz in the reproduced sound signal. Fig. 9B When generating a leakage sound signal by using the approximate characteristic CA13 shown in FIG. 1 , the leakage sound signal can be easily generated simply by uniformly attenuating the level of each frequency component in the reproduced sound signal by 2 dB.

[0134] In the transfer characteristic correction unit 132, it is assumed that the leakage sound signal is generated using the approximate characteristic CA13 as described above, which shows the case where the level of the frequency component lower than the reference frequency in the sound signal is a constant first level, and the level of the frequency component higher than the reference frequency is a second level different from the constant first level. In this case, the leakage sound signal can be easily generated by uniformly attenuating the level of the frequency component lower than the reference frequency in the reproduced sound signal by an amount corresponding to the absolute value of the first level and uniformly attenuating the level of the frequency component higher than the reference frequency in the reproduced sound signal by an amount corresponding to the absolute value of the second level.

[0135] Thus, according to the audio device 11A of the present modification, for example, the generation of the leakage sound signal in the second generator 22A can be easily realized by using a biquad filter based on an IIR (Infinite Impulse Response) filter. Figure 6 Compared with the audio device 11 shown in the figure, it is possible to reduce the size of the structure and the amount of calculation required for generating the leakage sound signal.

[0136] The above description includes audio systems 1 and 1A including audio devices 11 and 11A that perform signal processing on one-channel audio signal S output from sound source 10. However, audio signals of multiple channels such as two channels (stereo) are usually output from sound source 10 such as a CD player.

[0137] Therefore, the following describes an audio system including an audio device that processes audio signals of multiple channels output from a sound source 90. The following describes an audio system 1B including an audio device 11B that processes audio signals S1 and S2 of two channels (stereo) output from a sound source 90 as a representative of the audio system.

[0138] Fig.11 1 is a diagram showing an example of a configuration of an acoustic system 1B according to another modified example of the first embodiment. Fig.11 As shown, in the audio system 1B, the audio signal S1 (first reproduction signal) of the two-channel audio signals S1 and S2 output from the sound source 90 is reproduced by the speaker 2a (first speaker) after being subjected to signal processing by the audio device 11B. The audio signal S2 (second reproduction signal) is reproduced by the speaker 2b (second speaker) after being subjected to signal processing by the audio device 11B.

[0139] The reproduced sound (first reproduced sound) reproduced by the speaker 2a is mainly detected by the microphone 3a (first microphone) provided close to the speaker 2a. The reproduced sound (second reproduced sound) reproduced by the speaker 2b is mainly detected by the microphone 3b (second microphone) provided close to the speaker 2b. A detection sound signal (first detection sound signal) indicating the detection sound detected by the microphone 3a and a detection sound signal (second detection sound signal) indicating the detection sound detected by the microphone 3b are input to the audio device 11B.

[0140] In the audio system 1B, two reproduced sounds reproduced by the speakers 2a and 2b are listened to in the reproduction area 100 (common reproduction area) set at a position close to the two speakers 2a and 2b right in front of the two speakers 2a and 2b. The two reproduced sounds are not recognized in the non-reproduction areas 200a and 200b located outside the reproduction area 100. Therefore, the audio device 11B adjusts the levels of the two-channel audio signals S1 and S2 output by the sound source 90 using the detection sound signals detected by the microphones 3a and 3b.

[0141] Here, it is assumed that the frequency characteristics of the reproduced sound and the background noise at the representative point 201a (first representative point) in the non-reproduced area 200a and the representative point 201b (second representative point) in the non-reproduced area 200b are as follows: Figure 2As shown in FIG. 1 , in this case, since the reproduced sound of the frequency components above the frequency f1 is higher in level than the background noise, it is recognized by the person at the representative point 201a and the representative point 201b. On the other hand, the reproduced sound of the frequency components below the frequency f1 is lower in level than the background noise and is masked by the background noise, so it is not recognized.

[0142] For this reason, Figure 3 As shown, the audio device 11B performs signal processing to reduce the level of the frequency components above the frequency f1 in the two audio signals S1 and S2, similarly to the audio devices 11 and 11A. As a result, the level of the reproduced sound reproduced by the speakers 2a and 2b at the representative point 201a and the representative point 201b does not exceed the level of the background noise, and the reproduced sound is not recognized by the person at the representative point 201a and the representative point 201b.

[0143] When the above signal processing is performed in the audio device 11B, the level of the frequency components above the frequency f1 of the reproduced sound heard by the person in the reproduction area 100 is also reduced. However, since the reproduction area 100 is closer to the speaker 2a than the representative point 201a and closer to the speaker 2b than the representative point 201b, before performing the signal processing, for example, Figure 4 As shown in FIG. 1 , the level of the reproduced sound is sufficiently greater than the level of the background noise. Figure 5 As shown, after the above signal processing is performed, the reproduced sound in the reproduction area 100 will not be masked by the background noise and can be recognized by the person located in the reproduction area 100.

[0144] use Fig.12 The above-described signal processing performed in audio device 11B will be described in more detail. Fig.12 This is a diagram showing an example of a detailed configuration of an acoustic system 1B according to another modification of the first embodiment.

[0145] like Fig.12 As shown, in the audio system 1B, the audio device 11B functions as two first generating units 21a and 21b, two second generating units 22a and 22b, and an adjusting unit 20B. The first generating unit 21a includes a transfer characteristic correction unit 131a and a subtracting unit 14a, and the first generating unit 21b includes a transfer characteristic correction unit 131b and a subtracting unit 14b. The second generating unit 22a includes a transfer characteristic correction unit 132a, and the second generating unit 22b includes a transfer characteristic correction unit 132b. The adjusting unit 20B includes two correcting units 12a and 12b, four frequency analyzing units 151a, 152a, 151b, and 152b, two comparing units 16a and 16b, and a determining unit 17.

[0146] The two-channel audio signals S1 and S2 adjusted to the level corresponding to the volume set by the listener and outputted in the sound source 90 are inputted to the adjustment unit 20B. In the adjustment unit 20B, the correction unit 12a and the correction unit 12 ( Figure 6 ) Similarly, the audio signal S1, which is one of the two channels of audio signals S1 and S2 input, is adjusted to a level corresponding to a given initial value (for example, 0 dB), and the speaker 2a reproduces the adjusted audio signal S1. The microphone 3a detects a sound in which the reproduced sound reproduced by the speaker 2a and the background noise N around the microphone 3a are mixed, and outputs a detection sound signal representing the detected detection sound to the subtraction unit 14a.

[0147] The audio signal S1 is also input to the first generating unit 21a. Figure 6 ) Similarly, based on the input audio signal S1, the detection sound signal indicating the detection sound detected by the microphone 3a, and the transfer characteristic C11 (first characteristic) of the sound signal from the speaker 2a to the microphone 3a, a background noise signal (first background noise signal) indicating the ambient sound around the microphone 3a is generated. The first generating unit 21a outputs the generated background noise signal to the frequency analyzing unit 151a.

[0148] Specifically, in the first generation unit 21a, the transfer characteristic correction unit 131a and the transfer characteristic correction unit 131 ( Figure 6 ) Similarly, a signal after convolution processing is performed on the audio signal S1 using the coefficient "C11" that approximates the transfer characteristic C11 is generated as a reproduced sound signal representing the reproduced sound listened to at the installation position of the microphone 3a. The subtraction unit 14a generates a signal obtained by subtracting the reproduced sound signal generated by the transfer characteristic correction unit 131a from the detection sound signal representing the detection sound detected by the microphone 3a as a background noise signal representing the background noise around the microphone 3a.

[0149] The audio signal S1 is also input to the second generating unit 22a. The second generating unit 22a and the second generating unit 22 ( Figure 6 ) Similarly, based on the input audio signal S1 and the transfer characteristic C13 (first and second characteristics) of the sound signal from the speaker 2a to the representative point 201a, a leakage sound signal (first leakage sound signal) representing the reproduced sound heard at the representative point 201a is generated. The second generation unit 22a outputs the generated leakage sound signal to the frequency analysis unit 152a.

[0150] Specifically, in the second generation unit 22a, the transfer characteristic correction unit 132a and the transfer characteristic correction unit 132 ( Figure 6) Similarly, a signal is generated after the audio signal S1 is convolved with the coefficient "C13" that approximates the transfer characteristic C13, as a leakage signal representing the reproduced sound heard at the representative point 201a.

[0151] On the other hand, the audio signal S2 which is one of the input two-channel audio signals S1 and S2 is input to the correction unit 12b, the first generation unit 21b, and the second generation unit 22b.

[0152] The correction unit 12b adjusts the level to a given initial value (e.g., 0 dB) similarly to the correction unit 12a, and causes the speaker 2b to reproduce the adjusted audio signal S2. The microphone 3b detects a sound in which the reproduced sound reproduced by the speaker 2b and the background noise N around the microphone 3b are mixed, and outputs a detection sound signal representing the detected detection sound to the subtraction unit 14b.

[0153] The first generating unit 21b generates a background noise signal (second background noise signal) representing the ambient sound around the microphone 3b based on the input audio signal S2, the detection sound signal representing the detection sound detected by the microphone 3b, and the transfer characteristic C21 (second first characteristic) of the sound signal from the speaker 2b to the microphone 3b, similarly to the first generating unit 21a. The first generating unit 21b outputs the generated background noise signal to the frequency analyzing unit 151b.

[0154] Specifically, in the first generating unit 21b, the transfer characteristic modifying unit 131b generates a signal after convolution processing of the audio signal S2 using the coefficient "C21" that approximates the transfer characteristic C21, as the reproduced sound signal representing the reproduced sound heard at the installation position of the microphone 3b, similarly to the transfer characteristic modifying unit 131a. The subtracting unit 14b generates a signal obtained by subtracting the reproduced sound signal generated by the transfer characteristic modifying unit 131b from the detected sound signal representing the detected sound detected by the microphone 3b, as the background noise signal representing the background noise around the microphone 3b.

[0155] The second generation unit 22b generates a leakage sound signal (second leakage sound signal) representing the reproduced sound heard at the representative point 201b, similarly to the second generation unit 22a, based on the input audio signal S2 and the transfer characteristic C23 (second second characteristic) of the sound signal from the speaker 2b to the representative point 201b. The second generation unit 22b outputs the generated leakage sound signal to the frequency analysis unit 152b.

[0156] Specifically, in the second generating unit 22b, the transfer characteristic correction unit 132b, similarly to the transfer characteristic correction unit 132a, generates a signal after convolution processing of the audio signal S2 using the coefficient "C23" that approximates the transfer characteristic C23, as a leakage signal representing the reproduced sound heard at the representative point 201b.

[0157] The adjustment unit 20B adjusts the levels of the two audio signals S1 and S2 so that the level of the leakage sound signal generated by the second generation unit 22a is lower than the level of the background noise signal generated by the first generation unit 21a, and the level of the leakage sound signal generated by the second generation unit 22b is lower than the level of the background noise signal generated by the first generation unit 21b. The adjustment unit 20B causes the speaker 2a to reproduce the adjusted audio signal S1, and causes the speaker 2b to reproduce the adjusted audio signal S2.

[0158] Specifically, in the adjustment unit 20B, the frequency analysis unit 151a and the frequency analysis unit 151 ( Figure 6 ) Similarly, the level of each frequency component of the background noise signal generated by the first generating unit 21a is calculated. The frequency analyzing unit 152a and the frequency analyzing unit 152 ( Figure 6 ) Similarly, the levels of each frequency component of the leakage signal generated by the second generating unit 22a are calculated.

[0159] The comparison unit 16a compares the levels of each frequency component of the background noise signal calculated by the frequency analysis unit 151a with the levels of each frequency component of the leakage signal calculated by the frequency analysis unit 152a, and outputs the magnitude relationship and difference between the levels of each frequency component of the background noise signal and the levels of each frequency component of the leakage signal as a comparison result to the judgment unit 17.

[0160] The frequency analysis unit 151b calculates the level of each frequency component of the background noise signal generated by the first generation unit 21b, similarly to the frequency analysis unit 151a. The frequency analysis unit 152b calculates the level of each frequency component of the leakage sound signal generated by the second generation unit 22b, similarly to the frequency analysis unit 152a.

[0161] The comparison unit 16b compares the level of each frequency component of the background noise signal calculated by the frequency analysis unit 151b with the level of each frequency component of the leakage signal calculated by the frequency analysis unit 152b. The comparison unit 16b outputs the magnitude relationship and difference between the level of each frequency component of the background noise signal and the level of each frequency component of the leakage signal to the determination unit 17 as the comparison result.

[0162] The judgment unit 17 refers to the comparison result input from the comparison unit 16a, and determines the frequency component (hereinafter referred to as the first frequency component) in the leakage signal (hereinafter referred to as the first leakage signal) generated by the second generation unit 22a, which has a level greater than the background noise signal (hereinafter referred to as the first background noise signal) generated by the first generation unit 21a.

[0163] Similarly, the judgment unit 17 refers to the comparison result input from the comparison unit 16b to determine the frequency component (hereinafter referred to as the second frequency component) in the leakage signal (hereinafter referred to as the second leakage signal) generated by the second generation unit 22b, which has a level greater than the background noise signal (hereinafter referred to as the second background noise signal) generated by the first generation unit 21b.

[0164] The judgment unit 17 outputs information representing the determined first frequency component and second frequency component, the difference between the level of the first frequency component in the first background noise signal input from the comparison unit 16a and the level of the first frequency component in the first leakage sound signal, and the difference between the level of the second frequency component in the second background noise signal input from the comparison unit 16b and the level of the second frequency component in the second leakage sound signal, to the correction unit 12a and the correction unit 12b.

[0165] The correction unit 12a refers to the information input from the judgment unit 17 and attenuates the level of the frequency component (hereinafter referred to as the third frequency component) corresponding to the first frequency component or the second frequency component in the audio signal S1 by more than the larger of the difference between the level of the third frequency component in the first leakage sound signal and the level of the third frequency component in the first background noise signal and the difference between the level of the third frequency component in the second leakage sound signal and the level of the third frequency component in the second background noise signal.

[0166] The correction unit 12b, like the correction unit 12a, attenuates the level of the third frequency component in the audio signal S2 by more than the larger difference between the difference between the level of the third frequency component in the first leakage sound signal and the level of the third frequency component in the first background noise signal and the difference between the level of the third frequency component in the second leakage sound signal and the level of the third frequency component in the second background noise signal, with reference to the information input from the determination unit 17. In addition, the correction unit 12b attenuates the level of the third frequency component in the audio signal S2 by the same amount as the amount by which the correction unit 12a attenuates the level of the third frequency component in the audio signal S1.

[0167] For example, assuming that the first frequency component is a frequency component of frequency "f1", the difference between the level of the frequency component of frequency "f1" in the first leakage sound signal and the level of the frequency component of frequency "f1" in the first background noise signal is level "L11". On the other hand, assuming that the difference between the level of the frequency component of frequency "f1" in the second leakage sound signal and the level of the frequency component of frequency "f1" in the second background noise signal is level "L12" which is smaller than level "L11".

[0168] In addition, assuming that the second frequency component is a frequency component of frequency "f2", the difference between the level of the frequency component of frequency "f2" in the first leakage sound signal and the level of the frequency component of frequency "f2" in the first background noise signal is level "L21". On the other hand, assuming that the difference between the level of the frequency component of frequency "f2" in the second leakage sound signal and the level of the frequency component of frequency "f2" in the second background noise signal is level "L22" which is greater than level "L21".

[0169] In this case, the correction unit 12a uses the frequency component of the frequency "f1" in the audio signal S1 as the third frequency component, and attenuates the level of the frequency component of the frequency "f1" in the audio signal S1 by a level greater than the level "L11" by a given error level. On the other hand, the correction unit 12a uses the frequency component of the frequency "f2" in the audio signal S1 as the third frequency component, and attenuates the level of the frequency component of the frequency "f2" in the audio signal S1 by a level greater than the level "L22" by the above error level.

[0170] Similarly, the correction unit 12b uses the frequency component of the frequency "f1" in the audio signal S2 as the third frequency component, and attenuates the level of the frequency component of the frequency "f1" in the audio signal S2 by a level greater than the level "L11" by the error level. In addition, the correction unit 12b uses the frequency component of the frequency "f2" in the audio signal S2 as the third frequency component, and attenuates the level of the frequency component of the frequency "f2" in the audio signal S2 by a level greater than the level "L22" by the error level.

[0171] Alternatively, the correction unit 12a may not use the above error level, but may attenuate the level of the frequency component of the frequency "f1" in the audio signal S1 by the level "L11", and attenuate the level of the frequency component of the frequency f2 by the level "L22". Accordingly, the correction unit 12b may not use the above error level, but may attenuate the level of the frequency component of the frequency "f1" in the audio signal S2 by the level "L11", and attenuate the level of the frequency component of the frequency f2 by the level "L22".

[0172] The following describes the effects obtained by the structure of this modification. Figure 6) Similarly, it is assumed that the comparison result by the comparison unit 16a is input to the correction unit 12a, and the comparison result by the comparison unit 16b is input to the correction unit 12b. Furthermore, it is assumed that the correction unit 12a adjusts the level of the audio signal S1 based on the comparison result input from the comparison unit 16a, and the correction unit 12b adjusts the level of the audio signal S2 based on the comparison result input from the comparison unit 16b. In this case, if the adjustment degree of the level of the audio signal S1 is different from the adjustment degree of the level of the audio signal S2, there is a concern that the listener may not be able to feel the stereo reproduction of the two audio signals S1 and S2.

[0173] However, in the structure of this variant, both the correction unit 12a and the correction unit 12b make the following adjustments based on the same information input from the judgment unit 17: the level of the third frequency component in the two audio signals S1 and S2 is attenuated by an amount equal to or greater than the difference between the level of the third frequency component in the first leakage sound signal and the level of the third frequency component in the first background noise signal, and the difference between the level of the third frequency component in the second leakage sound signal and the level of the third frequency component in the second background noise signal. Therefore, in either of the non-reproduction areas 200a and 200b, the level of the reproduced sound is lower than the level of the background noise. Moreover, since the adjustment degree of the audio signal S1 in the correction unit 12a is the same as the adjustment degree of the audio signal S2 in the correction unit 12b, the listener can feel the stereo reproduction of the two audio signals S1 and S2 in the reproduction area 100.

[0174] In addition, the audio device 11 ( Figure 6 ) Similarly, the adjustment amount of the level of the audio signals S1 and S2 by the correction unit 12a and the correction unit 12b is calculated based on the level of the leakage signal representing the reproduced sound listened to at the representative point of the non-reproduction area 200a, 200b. Therefore, the structure of this modification example can adjust the level of the audio signals S1 and S2 to a level appropriate for the listener located in the reproduction area 100 without excessively attenuating the level.

[0175] Alternatively, the audio device 11A ( Fig.10 ) of the first generation unit 21A and the second generation unit 22A similarly constitute the acoustic device 11B ( Fig.12 ) of the first generation unit 21a and the second generation unit 22a. Similarly, the audio device 11A ( Fig.10 ) of the first generation unit 21A and the second generation unit 22A similarly constitute the acoustic device 11B ( Fig.12 ) of the first generating unit 21b and the second generating unit 22b. In these cases, it is possible to reduce the size of the structure and the amount of calculation required for generating the leakage sound signal.

[0176] (Second embodiment)

[0177] Next, an acoustic system 1C according to a second embodiment will be described. Fig.13 1 is a diagram showing an example of the configuration of an audio system 1C according to the second embodiment. Fig.13 As shown, the acoustic system 1C according to the second embodiment corresponds to the acoustic system 1B ( Fig.11 ) are arranged in close proximity, and include four speakers 2a to 2d, four microphones 3a to 3d, two audio devices 11Ba and 11Bb, and two sound sources 90a and 90b.

[0178] The audio system 1C involved in the second embodiment is used, for example, in the following situations: at two adjacent seats in a train or an airplane, or at two close seats such as a driver's seat and a front passenger seat in a car, the reproduced sound reproduced by the speakers installed in each seat can be listened to only in the reproduction area 100 set near the head of the seated occupant of each seat.

[0179] Fig.14A as well as Fig. 14B 1 is a diagram showing an example of the installation positions of four speakers 2a to 2d and four microphones 3a to 3d included in the audio system 1C. Fig.14A The example shown is one in which four speakers 2a to 2d are provided in the headrests of two adjacent seats whose seat backs are integrated into the headrests, which is used in seats of trains or the like. Fig. 14B The example of four speakers 2a to 2d in the headrests of two seats where the seat backs and headrests are separated and close to each other, which is used in the driver's seat and the front passenger seat of a car, is shown. Fig.14A as well as Fig. 14B As shown, four microphones 3a to 3d are provided on the side surfaces of the speakers 2a to 2d, respectively.

[0180] Fig.15A 1 is a front view showing another example of the installation positions of the four speakers 2a to 2d and the four microphones 3a to 3d included in the audio system 1C. Fig. 15B FIG. 2 is a top view showing another example. Fig.15A As shown in FIG. 1 , in the seat “seat 1” (first seat), two speakers 2a and 2b are arranged on the side of the seated person so as to sandwich the seated person’s head. In the seat “seat 2” (second seat), two speakers 2c and 2d are arranged on the side of the seated person so as to sandwich the seated person’s head. Fig. 15B As shown, the four speakers 2a to 2d are installed to protrude from the headrest, and the vibration plates of the four speakers 2a to 2d face the ears of the seated person. Fig.15A as well as Fig. 15BAs shown, four microphones 3a to 3d are provided on the back side of the speakers 2a to 2d, respectively.

[0181] The installation positions of the four microphones 3a to 3d are not limited to the above-mentioned installation positions, and may be any position close to the speakers 2a to 2d, such as a position close to the side surface of the diaphragm in the front baffle of each speaker 2a to 2d.

[0182] In addition, the two seats close to each other are not limited to seats in vehicles, but can also be seats in movie theaters, seats in theme park attractions, and seats in offices. In other words, as long as a plurality of seats with speakers provided on the headrests are arranged close to each other, they can be used.

[0183] like Fig.13 As shown, in the audio system 1C, the two-channel audio signals S1a and S2a output from the sound source 90a are processed by the audio device 11Ba and then reproduced by the speakers 2a and 2b. The two-channel audio signals S1b and S2b output from the sound source 90b are processed by the audio device 11Bb and then reproduced by the speakers 2c and 2d.

[0184] The reproduced sound reproduced by the speaker 2a is mainly detected by the microphone 3a, and the reproduced sound reproduced by the speaker 2b (first speaker) (first reproduced sound) is mainly detected by the microphone 3b (first microphone). The reproduced sound reproduced by the speaker 2c (second speaker) (second reproduced sound) is mainly detected by the microphone 3c (second microphone), and the reproduced sound reproduced by the speaker 2d is mainly detected by the microphone 3d.

[0185] The detection sound signal indicating the detection sound detected by the microphones 3a and 3b is input to the audio device 11Ba, and the detection sound signal indicating the detection sound detected by the microphones 3c and 3d is input to the audio device 11Bb.

[0186] In the audio system 1C, in the seat set to "Seat 1" ( Fig.14A , Fig. 14B or Fig.15A as well as Fig. 15B ) is located in a reproduction area 100a (first reproduction area) in front of the two speakers 2a and 2b and close to the two speakers 2a and 2b. The two reproduced sounds reproduced by the speakers 2a and 2b are listened to. In addition, in the seat "Seat 2" ( Fig.14A , Fig. 14B or Fig.15A as well as Fig. 15B) is located in a reproduction area 100b (second reproduction area) located near the two speakers 2c and 2d and directly in front of the two speakers 2c and 2d installed in the image display device, and two reproduced sounds reproduced by the speakers 2c and 2d are listened to.

[0187] However, for the seated person in the seat "seat 1", that is, the listener "listener A" located in the reproduction area 100a, hearing the reproduced sound reproduced by the speakers 2c and 2d is a problem. In addition, for the seated person in the seat "seat 2", that is, the listener "listener B" located in the reproduction area 100b, hearing the reproduced sound reproduced by the speakers 2a and 2b is a problem. In other words, for each listener, the reproduced sound heard by the seated person in the adjacent seat interferes with the reproduced sound heard by the listener. For this reason, in the audio system 1C, the reproduced sound leaked from other reproduction areas 100a and 100b close to the reproduction areas 100a and 100b where each listener is located is not recognized.

[0188] Therefore, in the sound system 1C, the microphones 3a and 3b are used to detect the reproduced sound reproduced by the speakers 2c and 2d leaking into the reproduction area 100a. The sound device 11Ba uses the detection sound signal representing the detection sound detected by the microphones 3a and 3b to adjust the level of the two-channel audio signals S1a and S2a output by the sound source 90a. Similarly, the microphones 3c and 3d are used to detect the reproduced sound reproduced by the speakers 2a and 2b leaking into the reproduction area 100b. The sound device 11Bb uses the detection sound signal representing the detection sound detected by the microphones 3c and 3d to adjust the level of the two-channel audio signals S1b and S2b output by the sound source 90b.

[0189] use Fig.16 The above-mentioned signal processing performed in the audio devices 11Ba and 11Bb will be described in more detail. Fig.16 This is a diagram showing an example of a detailed configuration of an acoustic system 1C according to another modification of the second embodiment.

[0190] Fig.16 Extract only Fig.13 The structure related to the two speakers 2b and 2c located between the listener "listener A" and the listener "listener B" in the audio system 1C. They are the structural elements closest to the listener "listener A" and the listener "listener B" in the audio system 1C, and the two reproduced sounds reproduced by the two speakers have a greater impact on each other's listeners than the structure related to the other two speakers 2a and 2d. Therefore, the following only describes in detail the structure and operation related to the two speakers 2b and 2c and the two microphones 3b and 3c, and omits the description of the structure and operation related to the other two speakers 2a and 2d and the two microphones 3a and 3d.

[0191] like Fig.16 As shown, the structure related to the two speakers 2b and 2c corresponds to the acoustic system 1 of the first embodiment ( Figure 6 )'s structure independently arranges the two structures.

[0192] The first generation unit 21b (transfer characteristic correction unit 131b, subtraction unit 14b), the second generation unit 22b (transfer characteristic correction unit 132b), and the adjustment unit 20Ba (frequency analysis unit 151b, frequency analysis unit 152b, comparison unit 16b, and correction unit 12b) of the acoustic device 11Ba associated with the speaker 2b are respectively connected to the acoustic device 11 ( Figure 6 )'s first generation unit 21 (transfer characteristic correction unit 131, subtraction unit 14), second generation unit 22 (transfer characteristic correction unit 132), and adjustment unit 20 (frequency analysis unit 151, frequency analysis unit 152, comparison unit 16, and correction unit 12) operate in the same manner.

[0193] The first generation unit 21c (transfer characteristic correction unit 131c, subtraction unit 14c), the second generation unit 22c (transfer characteristic correction unit 132c), and the adjustment unit 20Bb (frequency analysis unit 151c, frequency analysis unit 152c, comparison unit 16c, and correction unit 12c) of the audio device 11Bb related to the speaker 2c are also respectively connected to the audio device 11 ( Figure 6 )'s first generation unit 21 (transfer characteristic correction unit 131, subtraction unit 14), second generation unit 22 (transfer characteristic correction unit 132), and adjustment unit 20 (frequency analysis unit 151, frequency analysis unit 152, comparison unit 16, and correction unit 12) operate in the same manner.

[0194] In addition, the audio device 11Ba and the audio device 11Bb may be configured by the same computer, or may be configured by separate computers.

[0195] Specifically, the audio signal S2a (first reproduced signal) adjusted to a level corresponding to the volume set by the listener "listener A" in the sound source 90a and outputted is inputted to the adjustment unit 20Ba. In the adjustment unit 20Ba, the correction unit 12b adjusts the audio signal S2a to a level corresponding to a given initial value (for example, 0 dB), and causes the speaker 2b to reproduce the adjusted audio signal S2a. The microphone 3b detects a sound in which the reproduced sound reproduced by the speaker 2b and the background noise N around the microphone 3b are mixed, and outputs a detection sound signal (first detection sound signal) indicating the detected detection sound to the subtraction unit 14b.

[0196] The audio signal S2a output from the sound source 90a is also input to the first generating unit 21b. The first generating unit 21b generates a background noise signal (first background noise signal) representing the ambient sound around the microphone 3b based on the input audio signal S2a, the detection sound signal representing the detection sound detected by the microphone 3b, and the transfer characteristic (first transfer characteristic) of the sound signal from the speaker 2b to the microphone 3b.

[0197] Specifically, in the first generating unit 21b, the transfer characteristic modifying unit 131b performs convolution processing on the input audio signal S2a using the coefficient "C21", thereby generating the signal after the convolution processing as a reproduced sound signal representing the reproduced sound heard at the installation position of the microphone 3b. The transfer characteristic modifying unit 131b outputs the generated reproduced sound signal to the subtracting unit 14b.

[0198] Here, the coefficient "C21" is a coefficient that approximates the transfer characteristic of the sound signal from the speaker 2b to the microphone 3b. The coefficient "C21" is predetermined based on the detection sound signal representing the detection sound detected by the microphone 3b when the speaker 2b reproduces the sound signal for the experiment, for example. Hereinafter, the coefficient "C21" may be described as the transfer characteristic C21 from the speaker 2b to the microphone 3b.

[0199] The subtracting unit 14b generates a signal obtained by subtracting the reproduced sound signal generated by the transfer characteristic correction unit 131b from the detected sound signal indicating the detected sound detected by the microphone 3b as a background noise signal indicating the background noise around the microphone 3b.

[0200] Specifically, the detection sound signal representing the detection sound detected by the microphone 3b can be expressed as "C21·S2a+N", and the reproduced sound signal generated by the transfer characteristic correction unit 131b can be expressed as "C21·S2a". Here, "S2a" represents the audio signal S2a. "N" is a sound signal representing the background noise N around the microphone 3b. The subtraction unit 14b generates a sound signal "N (=C21·S2a+N-C21·S)" obtained by subtracting the reproduced sound signal "C21·S2a" from the detection sound signal "C21·S2a+N", as a background noise signal representing the background noise around the microphone 3b.

[0201] The audio signal S2a output from the sound source 90a is also input to the second generation unit 22b. The second generation unit 22b generates a leakage sound signal (first leakage sound signal) representing the reproduced sound heard at the representative point 201b (first representative point) based on the input audio signal S2a and the transfer characteristic (third transfer characteristic) of the sound signal from the speaker 2b to the representative point 201b (first representative point) located in the reproduction area 100b. The representative point 201b may be, for example, a position within the reproduction area 100b such as the position of the right ear of the listener "listener B" who listens to the reproduced sound reproduced by the speaker 2c.

[0202] Specifically, in the second generation unit 22b, the transfer characteristic correction unit 132b performs convolution processing on the input audio signal S2a using the coefficient "C23", thereby generating a sound signal "C23·S2a" after the convolution processing as a leakage sound signal representing the reproduced sound heard at the representative point 201b.

[0203] Here, the coefficient "C23" is a coefficient that approximates the transfer characteristic of the sound signal from the speaker 2b to the representative point 201b. The coefficient "C23" is predetermined based on the detection sound signal representing the detection sound detected by the microphone located at the representative point 201b, for example, when the speaker 2b reproduces the sound signal for the experiment. In the following, the coefficient "C23" is sometimes described as the transfer characteristic C23 from the speaker 2 to the representative point 201b.

[0204] The adjustment unit 20Ba adjusts the level of the audio signal S2a so that the level of the leakage sound signal generated by the second generation unit 22b is lower than the level of the background noise signal generated by the first generation unit 21b. The adjustment unit 20Ba causes the speaker 2b to reproduce the adjusted audio signal S2a.

[0205] Specifically, in the adjustment unit 20Ba, the frequency analysis unit 151b calculates the level of each frequency component of the background noise signal generated by the first generation unit 21b by performing a given frequency analysis process such as fast Fourier transform (FFT). The frequency analysis unit 152b calculates the level of each frequency component of the leakage sound signal generated by the second generation unit 22b in the same manner as the frequency analysis unit 151b.

[0206] The comparison unit 16b compares the levels of each frequency component of the background noise signal calculated by the frequency analysis unit 151b and the levels of each frequency component of the leakage signal calculated by the frequency analysis unit 152b, and outputs the magnitude relationship between the levels of each frequency component of the background noise signal and the levels of each frequency component of the leakage signal and the difference as the comparison result to the correction unit 12b.

[0207] The correction unit 12b adjusts the level of the audio signal S2a input from the sound source 90a based on the comparison result input from the comparison unit 16b so that the level of the leakage sound signal is lower than the level of the background noise signal. The correction unit 12b causes the speaker 2b to reproduce the adjusted audio signal S2a.

[0208] Specifically, the correction unit 12b, like the correction unit 12 of the first embodiment, attenuates the level of the frequency component corresponding to the object frequency component in the audio signal S2a by more than the difference between the level of the object frequency component in the leakage signal that is greater than the level of the background noise signal and the level of the frequency component corresponding to the object frequency component in the background noise signal.

[0209] That is, the adjustment unit 20Ba does not compare the reproduced sound detected by the microphone 3b with a higher level with the background noise signal, but compares the leakage sound signal representing the reproduced sound listened to at the representative point 201b with the background noise signal to adjust the audio signal S2a, so that the level of the audio signal S2a can be adjusted appropriately without excessively adjusting the level. As a result, the listener "listener A" can listen to the reproduced sound reproduced by the speaker 2b in the reproduction area 100a. In addition, the level of the reproduced sound listened to at the representative point 201b in the reproduction area 100b represented by the leakage sound signal can be made lower than the level of the ambient sound around the microphone 3b represented by the background noise signal, thereby preventing the listener "listener B" located in the reproduction area 100b from recognizing the reproduced sound reproduced by the speaker 2b.

[0210] Furthermore, when the microphone 3c is installed close to the speaker 2c and the representative point 201b, the transfer characteristic C23 may be used as the transfer characteristic of the sound signal from the speaker 2b to the microphone 3c. In this case, the coefficient "C23" used by the second generator 22b to generate the leakage sound signal can be determined using the microphone 3c without taking the trouble of moving the installation position of the microphone 3c or installing a microphone other than the microphone 3c at the representative point 201b.

[0211] Similarly, the audio signal S1b (second reproduced signal) adjusted to a level corresponding to the volume set by the listener "listener B" in the sound source 90b and outputted is inputted to the adjustment unit 20Bb. In the adjustment unit 20Bb, the correction unit 12c adjusts the audio signal S1b to a level corresponding to a given initial value (for example, 0 dB), and causes the speaker 2c to reproduce the adjusted audio signal S1b. The microphone 3c detects a sound in which the reproduced sound reproduced by the speaker 2c and the background noise N around the microphone 3c are mixed, and outputs a detection sound signal (second detection sound signal) indicating the detected detection sound to the subtraction unit 14c.

[0212] The audio signal S1b output from the sound source 90b is also input to the first generating unit 21c. The first generating unit 21c generates a background noise signal (second background noise signal) representing the ambient sound around the microphone 3c based on the input audio signal S1b, the detection sound signal representing the detection sound detected by the microphone 3c, and the transfer characteristic (second transfer characteristic) of the sound signal from the speaker 2c to the microphone 3c.

[0213] Specifically, in the first generation unit 21c, the transfer characteristic correction unit 131c performs convolution processing on the input audio signal S1b using the coefficient "C31", thereby generating the signal after the convolution processing as a reproduced sound signal representing the reproduced sound heard at the installation position of the microphone 3c. The transfer characteristic correction unit 131c outputs the generated reproduced sound signal to the subtraction unit 14c.

[0214] Here, the coefficient "C31" is a coefficient that approximates the transfer characteristic of the sound signal from the speaker 2c to the microphone 3c. The coefficient "C31" is predetermined based on the detection sound signal representing the detection sound detected by the microphone 3c when the speaker 2c reproduces the sound signal for the experiment, for example. Hereinafter, the coefficient "C31" may be described as the transfer characteristic C31 from the speaker 2c to the microphone 3c.

[0215] The subtracting unit 14c generates a signal obtained by subtracting the reproduced sound signal generated by the transfer characteristic correction unit 131c from the detected sound signal indicating the detected sound detected by the microphone 3c as a background noise signal indicating the background noise around the microphone 3c.

[0216] Specifically, the detection sound signal representing the detection sound detected by the microphone 3c can be expressed as "C31·S1b+N", and the reproduced sound signal generated by the transfer characteristic correction unit 131c can be expressed as "C31·S1b". Here, "S1b" represents the audio signal S1b. "N" is a sound signal representing the background noise N around the microphone 3c. The subtraction unit 14c generates a sound signal "N (=C31·S1b+N-C31·S1b)" obtained by subtracting the reproduced sound signal "C31·S1b" from the detection sound signal "C31·S1b+N" as a background noise signal representing the background noise around the microphone 3c.

[0217] The audio signal S1b output from the sound source 90b is also input to the second generation unit 22c. The second generation unit 22c generates a leakage sound signal (second leakage sound signal) representing the reproduced sound heard at the representative point 201a (second representative point) based on the input audio signal S1b and the transfer characteristic (fourth transfer characteristic) of the sound signal from the speaker 2c to the representative point 201a (second representative point) located in the reproduction area 100a. The representative point 201a may be, for example, a position in the reproduction area 100a such as the position of the left ear of the listener "listener A" who listens to the reproduced sound reproduced by the speaker 2b.

[0218] Specifically, in the second generation unit 22c, the transfer characteristic correction unit 132c performs convolution processing on the input audio signal S1b using the coefficient "C33", thereby generating a sound signal "C33·S1b" after the convolution processing as a leakage sound signal representing the reproduced sound heard at the representative point 201a.

[0219] Here, the coefficient "C33" is a coefficient that approximates the transfer characteristic of the sound signal from the speaker 2c to the representative point 201a. The coefficient "C33" is predetermined based on the detection sound signal representing the detection sound detected by the microphone located at the representative point 201a, for example, when the speaker 2c reproduces the sound signal for the experiment. In the following, the coefficient "C33" is sometimes described as the transfer characteristic C33 from the speaker 2c to the representative point 201a.

[0220] The adjustment unit 20Bb adjusts the level of the audio signal S1b so that the level of the leakage sound signal generated by the second generation unit 22c is lower than the level of the background noise signal generated by the first generation unit 21c. The adjustment unit 20Bb causes the speaker 2c to reproduce the adjusted audio signal S1b.

[0221] Specifically, in the adjustment unit 20Bb, the frequency analysis unit 151c calculates the level of each frequency component of the background noise signal generated by the first generation unit 21c by performing a given frequency analysis process such as fast Fourier transform (FFT). The frequency analysis unit 152c calculates the level of each frequency component of the leakage sound signal generated by the second generation unit 22c in the same manner as the frequency analysis unit 151c.

[0222] The comparison unit 16c compares the levels of each frequency component of the background noise signal calculated by the frequency analysis unit 151c and the levels of each frequency component of the leakage signal calculated by the frequency analysis unit 152c, and outputs the size relationship and difference between the levels of each frequency component of the background noise signal and the levels of each frequency component of the leakage signal as the comparison result to the correction unit 12c.

[0223] The correction unit 12c adjusts the level of the audio signal S1b input from the sound source 90b based on the comparison result input from the comparison unit 16c so that the level of the leakage sound signal is lower than the level of the background noise signal. The correction unit 12c causes the speaker 2c to reproduce the adjusted audio signal S1b.

[0224] Specifically, the correction unit 12c, like the correction unit 12 of the first embodiment, attenuates the level of the frequency component corresponding to the object frequency component in the audio signal S1b by more than the difference between the level of the object frequency component in the leakage signal that is greater than the level of the background noise signal and the level of the frequency component corresponding to the object frequency component in the background noise signal.

[0225] That is, the adjustment unit 20Bb does not compare the reproduced sound detected by the microphone 3c with the background noise signal, but compares the leakage sound signal representing the reproduced sound listened to at the representative point 201a with the background noise signal to adjust the audio signal S1b, so that the level of the audio signal S1b can be adjusted appropriately without excessively adjusting the level. As a result, the listener "listener B" can listen to the reproduced sound reproduced by the speaker 2c in the reproduction area 100b. In addition, the level of the reproduced sound listened to at the representative point 201a of the reproduction area 100a represented by the leakage sound signal can be made lower than the level of the ambient sound around the microphone 3c represented by the background noise signal, thereby preventing the listener "listener A" located in the reproduction area 100a from recognizing the reproduced sound reproduced by the speaker 2c.

[0226] Furthermore, when the microphone 3b is installed close to the loudspeaker 2b and the representative point 201a, the transfer characteristic C33 may be used as the transfer characteristic of the sound signal from the loudspeaker 2c to the microphone 3b. In this case, the coefficient "C33" used by the second generator 22c to generate the leakage sound signal can be determined using the microphone 3b without taking the trouble of moving the installation position of the microphone 3b or installing a microphone other than the microphone 3b at the representative point 201a.

[0227] The flow of the above-mentioned signal processing performed in each of the audio devices 11Ba and 11Bb is the same as Figure 7 The process shown is the same, so the detailed description is omitted.

[0228] In addition, at the beginning of the description of the second embodiment described above, it is described that the acoustic system 1C corresponds to the acoustic system 1B ( Fig.11 ) are arranged close to each other. However, in Fig.16 In the example, the determination unit 17 ( Fig.12) Except for the structure associated with the two speakers 2b, 2c and the two microphones 3b, 3c.

[0229] For this purpose, the audio device 11Ba may not actually function as the determination unit 17 ( Fig.12 ) function, the correction unit 12a of the audio device 11Ba adjusts the level of the audio signal S1a based on the comparison result input from the comparison unit 16a, and the correction unit 12b adjusts the level of the audio signal S1b based on the comparison result input from the comparison unit 16b with an adjustment degree independent of the correction unit 12a. The same is true for the audio device 11Bb. However, in this structure, although it is possible to prevent the listener from recognizing the reproduced sound that is listened to by other listeners, there is a concern that the listener cannot feel the stereo reproduction.

[0230] Therefore, it is preferable that the determination unit 17 is not excluded from each of the audio devices 11Ba and 11Bb, and the audio devices 11Ba and 11Bb respectively perform the operation described in the modification of the first embodiment. In this case, the determination unit 17 of the audio device 11Ba outputs information necessary for adjustment of the correction unit 12a and the correction unit 12b to the correction unit 12a and the correction unit 12b based on the comparison result input from the comparison unit 16a and the comparison unit 16b. As a result, the correction unit 12a and the correction unit 12b adjust the level of the third frequency component of the audio signal S1a and the audio signal S2a by the same amount. The same is true for the audio device 11Bb.

[0231] Alternatively, the first generation unit 21b and the second generation unit 22b of the sound device 11Ba may be combined with the sound device 11A ( Fig.10 ) are configured similarly to the first generation unit 21A and the second generation unit 22A of the audio device 11Bc. Similarly, the first generation unit 21c and the second generation unit 22c of the audio device 11Bc may be configured similarly to the first generation unit 21A and the second generation unit 22A of the audio device 11A ( Fig.10 ) is configured similarly to the first generation unit 21A and the second generation unit 22A. In these cases, it is possible to reduce the size of the structure and the amount of calculation required for generating the leakage sound signal.

[0232] The sound system 1C of the second embodiment can also be applied to the following case, for example, in which three or more seats are arranged close to each other, such as passenger seats in trains and aircraft, so that only the reproduction area set near the head of the seated person in each seat can hear the reproduced sound reproduced by the speaker installed in each seat. For example, in the case of three or more seats arranged close to each other, so that only the reproduction area set near the head of the seated person in each seat can hear the reproduced sound reproduced by the speaker installed in each seat. Fig.17 As shown, it is sufficient to construct two audio systems 1Ca and 1Cb. Fig.17This is a diagram showing an example in which the acoustic system 1C according to the second embodiment is applied to three seats.

[0233] because Fig.17 The relationship between the listener "Listener A" and the listener "Listener B" shown is the same as Fig.13 The relationship between the listener "listener A" and the listener "listener B" shown is the same, so the operation of the audio system 1Ca is the same as that of the user. Fig.16 The operation of the audio system 1C described above may be the same.

[0234] In addition, since the relationship between listener "Listener B" and listener "Listener C" is also related to Fig.13 The relationship between the listener "listener A" and the listener "listener B" shown is the same, so the operation of the audio system 1Cb is the same as that of the user. Fig.16 The operation of the audio system 1C described above may be the same.

[0235] In other words, think Fig.17 The listener "Listener B" is equivalent to Fig.16 Listener "Listener A", Fig.17 The listener "Listener C" is equivalent to Fig.16 The listener "Listener B" is OK. Fig.17 The representative point 201c in the reproduction area 100b where the listener "listener B" exists is equivalent to Fig.16 The representative point 201a of the listener "Listener A" is sufficient. It is considered that the representative point 201d in the reproduction area 100c where the listener "Listener C" exists is equivalent to Fig.16 The representative point 201b in the reproduction area 100b where the listener "listener B" exists is sufficient. Fig.16 The operation of the audio system 1C described above may be the same.

[0236] As mentioned above, you can also Fig.11 The structure of the audio system 1B for one listener shown in the figure is applicable to the following Fig.13 The audio system 1C shown is for two listeners. Fig.11 The structure of the audio system 1B for a single listener shown in the figure is applicable to Fig.17 The case of the acoustic systems 1Ca and 1Cb for three listeners shown above is similarly applicable to an acoustic system for more than three listeners.

[0237] The technology disclosed herein does not use a speaker array, and can normally listen to the reproduced sound in the reproduction area, and can avoid recognizing the reproduced sound leaking outside the reproduction area. Therefore, the technology disclosed herein is useful in allowing the seated person in a plurality of seats close to each other, such as passenger seats in trains and aircraft, to listen to only the reproduced sound reproduced by the speakers installed in each seat.

Claims

1. An audio device that adjusts reproduced sound so that the reproduced sound reproduced by a speaker can be heard in a given reproduction area. The audio device comprises: a first generating unit that generates a background noise signal representing ambient sound around the microphone based on a reproduction signal output from a sound source of the reproduction sound, a detection sound signal representing a detection sound detected by a microphone disposed near the speaker, and a first characteristic that is a transfer characteristic of a sound signal from the speaker to the microphone; a second generating unit for generating a leakage sound signal representing the reproduced sound heard at the representative point based on the reproduced signal and a second characteristic which is a transfer characteristic of a sound signal from the speaker to a representative point located outside the reproduction area; and The adjustment unit adjusts the level of the reproduced signal so that the level of the leakage sound signal is lower than the level of the background noise signal.

2. The audio device according to claim 1, wherein: The adjustment unit calculates the difference between the level of the object frequency component in the leakage signal, which is greater than the level of the frequency component of the background noise signal, and the level of the frequency component in the background noise signal corresponding to the object frequency component, i.e., the difference level, so that the level of the frequency component corresponding to the object frequency component in the regenerated signal is attenuated by more than the difference level.

3. The audio device according to claim 1 or 2, wherein: The first generation unit performs the following processing: generating a reproduced sound signal representing the reproduced sound heard at the installation position of the microphone based on the reproduced signal and the first characteristic, generating a signal obtained by subtracting the reproduced sound signal from the detected sound signal as the background noise signal, The second generation unit performs the following processing: The leakage sound signal is generated based on the reproduced sound signal and an approximate characteristic obtained by approximating a difference characteristic between the first characteristic and the second characteristic.

4. The audio device according to claim 3, wherein: The approximate characteristic shows that the levels of each of the plurality of frequency components in the sound signal are constant.

5. The audio device according to claim 3, wherein: The approximate characteristic shows that the level of frequency components lower than a given reference frequency component in the sound signal is a constant first level, and the level of frequency components higher than the reference frequency component in the sound signal is a constant second level different from the first level.

6. An audio device that adjusts a first reproduced sound and a second reproduced sound so that the first reproduced sound reproduced by a first speaker is heard in a given first reproduction area, and the second reproduced sound reproduced by a second speaker is heard in a given second reproduction area, The first speaker is installed at the first seat. The second speaker is installed at a second seat close to the first seat. The audio device includes a first generating unit, a second generating unit, and an adjusting unit. The first generation unit performs the following processing: generating a first background noise signal representing ambient sound around the first microphone based on a first reproduction signal output from a sound source of the first reproduction sound, a first detection sound signal representing detection sound detected by a first microphone provided near the first speaker, and a first transfer characteristic being a transfer characteristic of a sound signal from the first speaker to the first microphone, generating a second background noise signal representing ambient sound around the second microphone based on a second reproduction signal output from a sound source of the second reproduction sound, a second detection sound signal representing detection sound detected by a second microphone provided near the second speaker, and a second transfer characteristic being a transfer characteristic of a sound signal from the second speaker to the second microphone, The second generation unit performs the following processing: generating a first leakage sound signal representing the first reproduced sound heard at the first representative point based on the first reproduced signal and a third transfer characteristic that is a transfer characteristic of a sound signal from the first speaker to a first representative point located in the second reproduced area, generating a second leakage sound signal representing the second reproduced sound heard at the second representative point based on the second reproduced signal and a fourth transfer characteristic that is a transfer characteristic of a sound signal from the second speaker to a second representative point located in the first reproduced area, The adjustment unit performs the following processing: The level of the first regenerated signal is adjusted so that the level of the first leakage sound signal is less than the level of the first background noise signal. The level of the second reproduced signal is adjusted so that the level of the second leakage sound signal is lower than the level of the second background noise signal.

7. The audio device according to claim 6, wherein: The adjustment unit performs the following processing: a first difference level is calculated as a difference between the level of the first frequency component, which is a frequency component of the first leakage signal having a level greater than that of the first background noise signal, and the level of the frequency component corresponding to the first frequency component in the first background noise signal, and the level of the frequency component corresponding to the first frequency component in the first regenerated signal is attenuated by more than the first difference level; A second difference level is calculated as the difference between the level of the second frequency component, which is the frequency component of the second leakage signal and has a level greater than that of the second background noise signal, and the level of the frequency component corresponding to the second frequency component in the second background noise signal, so that the level of the frequency component corresponding to the second frequency component in the second regenerated signal is attenuated by more than the second difference level.

8. The audio device according to claim 6 or 7, wherein: The first generation unit performs the following processing: generating a first reproduced sound signal representing the first reproduced sound heard at the installation position of the first microphone based on the first reproduced signal and the first transfer characteristic, generating a signal obtained by subtracting the first reproduced sound signal from the first detected sound signal as the first background noise signal, generating a second reproduced sound signal representing the second reproduced sound heard at the installation position of the second microphone based on the second reproduced signal and the second transfer characteristic; generating a signal obtained by subtracting the second reproduced sound signal from the second detected sound signal as the second background noise signal, The second generation unit performs the following processing: generating the first leakage sound signal based on the first reproduced sound signal and a first approximation characteristic that approximates a difference characteristic between the first transfer characteristic and the third transfer characteristic, The second leakage sound signal is generated based on the second reproduced sound signal and a second approximate characteristic that approximates a difference characteristic between the second transfer characteristic and the fourth transfer characteristic.

9. The audio device according to claim 8, wherein: The first approximate characteristic and the second approximate characteristic indicate that the levels of the plurality of frequency components in the audio signal are constant.

10. The audio device according to claim 8, wherein: The first approximate characteristic and the second approximate characteristic show that the level of the frequency component in the sound signal lower than a given reference frequency component is a constant first level, and the level of the frequency component in the sound signal higher than the reference frequency component is a constant second level different from the first level.

11. The audio device according to claim 6, wherein: The first representative point is a position where the second microphone is set. The second representative point is a position where the first microphone is installed.

12. The audio device according to claim 1, wherein The speakers include a first speaker and a second speaker disposed at the same seat, The reproduction area includes a common reproduction area for listening to the first reproduced sound reproduced by the first speaker and the second reproduced sound reproduced by the second speaker, The representative points include a first representative point and a second representative point located outside the common regeneration area, The microphone includes: a first microphone, which is arranged close to the first speaker; and a second microphone, which is arranged close to the second speaker. The first characteristic includes a first first characteristic which is a transfer characteristic of a sound signal from the first speaker to the first microphone, and a second first characteristic which is a transfer characteristic of a sound signal from the second speaker to the second microphone. The second characteristic includes a first second characteristic which is a transfer characteristic of the sound signal from the first speaker to the first representative point, and a second second characteristic which is a transfer characteristic of the sound signal from the second speaker to the second representative point. The first generation unit performs the following processing: generating a first background noise signal representing ambient sound around the first microphone based on a first reproduction signal output from a sound source of the first reproduction sound, a first detection sound signal representing detection sound detected by the first microphone, and the first first characteristic; generating a second background noise signal representing ambient sound around the second microphone based on a second reproduction signal output from a sound source of the second reproduction sound, a second detection sound signal representing detection sound detected by the second microphone, and the second first characteristic; The second generation unit performs the following processing: generating a first leakage sound signal representing the first reproduced sound heard at the first representative point based on the first reproduced signal and the first and second characteristics; generating a second leakage sound signal representing the second reproduced sound heard at the second representative point based on the second reproduced signal and the second second characteristic; The adjustment unit adjusts the levels of the first reproduced signal and the second reproduced signal so that the level of the first leakage sound signal is lower than the level of the first background noise signal, and the level of the second leakage sound signal is lower than the level of the second background noise signal.

13. The sound device according to claim 12, wherein: The adjustment unit performs the following processing: determining, in the first leakage sound signal, a first frequency component which is a frequency component having a level greater than that of the first background noise signal, determining, in the second leakage sound signal, a second frequency component whose level is greater than that of the frequency component of the second background noise signal, The level of the third frequency component, which is the frequency component corresponding to the first frequency component or the second frequency component in the first regenerated signal and the second regenerated signal, is attenuated by more than the larger of the difference between the level of the third frequency component in the first leakage signal and the level of the third frequency component in the first background noise signal, and the difference between the level of the third frequency component in the second leakage signal and the level of the third frequency component in the second background noise signal.

14. A reproduction method, the method being a reproduction method in an audio device, the audio device adjusting a reproduced sound so that the reproduced sound reproduced by a speaker can be heard in a given reproduction area, In the regeneration method, generating a background noise signal representing ambient sound around the microphone based on a reproduction signal output from a sound source of the reproduction sound, a detection sound signal representing detection sound detected by a microphone provided near the speaker, and a first characteristic being a transfer characteristic of a sound signal from the speaker to the microphone, generating a leakage sound signal representing the reproduced sound heard at the representative point based on the reproduced signal and a second characteristic that is a transfer characteristic of a sound signal from the speaker to a representative point located outside the reproduction area, The level of the regenerated signal is adjusted so that the level of the leakage signal is lower than the level of the background noise signal.

15. A program for causing a computer of an audio device to execute processing, wherein the audio device adjusts reproduced sound so that the reproduced sound reproduced by a speaker can be heard in a given reproduction area. The program causes the computer to execute the following processing: generating a background noise signal representing ambient sound around the microphone based on a reproduction signal output from a sound source of the reproduction sound, a detection sound signal representing detection sound detected by a microphone provided near the speaker, and a first characteristic being a transfer characteristic of a sound signal from the speaker to the microphone, generating a leakage sound signal representing the reproduced sound heard at the representative point based on the reproduced signal and a second characteristic that is a transfer characteristic of a sound signal from the speaker to a representative point located outside the reproduction area, The level of the regenerated signal is adjusted so that the level of the leakage signal is lower than the level of the background noise signal.

16. A reproduction method, the reproduction method being in an audio device, the audio device adjusting a first reproduced sound and a second reproduced sound so that the first reproduced sound reproduced by a first speaker is listened to in a given first reproduction area, and the second reproduced sound reproduced by a second speaker is listened to in a given second reproduction area, The first speaker is installed at the first seat. The second speaker is installed at a second seat close to the first seat. In the regeneration method, generating a first background noise signal representing ambient sound around the first microphone based on a first reproduction signal output from a sound source of the first reproduction sound, a first detection sound signal representing detection sound detected by a first microphone provided near the first speaker, and a first transfer characteristic being a transfer characteristic of a sound signal from the first speaker to the first microphone, generating a second background noise signal representing ambient sound around the second microphone based on a second reproduction signal output from a sound source of the second reproduction sound, a second detection sound signal representing detection sound detected by a second microphone provided near the second speaker, and a second transfer characteristic being a transfer characteristic of a sound signal from the second speaker to the second microphone, generating a first leakage sound signal representing the first reproduced sound heard at the first representative point based on the first reproduced signal and a third transfer characteristic that is a transfer characteristic of a sound signal from the first speaker to a first representative point located in the second reproduced area, generating a second leakage sound signal representing the second reproduced sound heard at the second representative point based on the second reproduced signal and a fourth transfer characteristic that is a transfer characteristic of a sound signal from the second speaker to a second representative point located in the first reproduced area, The level of the first regenerated signal is adjusted so that the level of the first leakage sound signal is less than the level of the first background noise signal. The level of the second reproduced signal is adjusted so that the level of the second leakage sound signal is lower than the level of the second background noise signal.

17. A program for causing a computer of an audio device to execute processing, wherein the audio device adjusts a first reproduced sound and a second reproduced sound so that the first reproduced sound reproduced by a first speaker is heard in a given first reproduction area, and the second reproduced sound reproduced by a second speaker is heard in a given second reproduction area, The first speaker is installed at the first seat. The second speaker is installed at a second seat close to the first seat. The program causes the computer to execute the following processing: generating a first background noise signal representing ambient sound around the first microphone based on a first reproduction signal output from a sound source of the first reproduction sound, a first detection sound signal representing detection sound detected by a first microphone provided near the first speaker, and a first transfer characteristic being a transfer characteristic of a sound signal from the first speaker to the first microphone, generating a second background noise signal representing ambient sound around the second microphone based on a second reproduction signal output from a sound source of the second reproduction sound, a second detection sound signal representing detection sound detected by a second microphone provided near the second speaker, and a second transfer characteristic being a transfer characteristic of a sound signal from the second speaker to the second microphone, generating a first leakage sound signal representing the first reproduced sound heard at the first representative point based on the first reproduced signal and a third transfer characteristic that is a transfer characteristic of a sound signal from the first speaker to a first representative point located in the second reproduced area, generating a second leakage sound signal representing the second reproduced sound heard at the second representative point based on the second reproduced signal and a fourth transfer characteristic that is a transfer characteristic of a sound signal from the second speaker to a second representative point located in the first reproduced area, The level of the first regenerated signal is adjusted so that the level of the first leakage sound signal is less than the level of the first background noise signal. The level of the second reproduced signal is adjusted so that the level of the second leakage sound signal is lower than the level of the second background noise signal.

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