Sound field control system and sound field control method

Abstract

The present invention addresses the problem of providing a sound field control system and a sound field control method that make it difficult for other people to listen to sound to be listened. [Solution] A boundary sound field control (a1, a2) for listening to a target sound is performed such that the sound pressure and the sound pressure gradient (sound pressure slope) are as zero as possible at a boundary BA1, which is the boundary between a range UA, which is assumed to be a range of movement of the head of a user, and a region A1 of a closed space of a speaker (1). Boundary sound field control (b1, b2) of the masking sound is performed such that the sound pressure and the sound pressure gradient (sound pressure slope) are zero at a boundary BA2U (solid line) on the range UA side among boundaries of a region A2 that does not include the range UA but includes the speaker (1), and propagate to the outside through a boundary BA2N (dotted line) on the range UA side.

Description

Technical Field

[0001] The present invention relates to a technology for controlling a sound field so that a sound to be listened to by a user, that is, a listening target sound, can be listened to only by the user. Background Art

[0002] As a technology for controlling the sound field so that the sound to be listened to by the user, that is, the listening object sound, can only be heard by the user, the following local reproduction technology is known: using the boundary sound field control technology based on the Kirchhoff-Helmholtz integral equation, the listening object sound is output from the speaker so that the sound pressure and sound pressure gradient of the listening object sound at the boundary of the first area where the user is located become 0, thereby minimizing the size of the listening object sound propagating outside the first area (for example, patent documents 1 and 2).

[0003] In addition, as a technology for controlling the sound field so that the sound to be listened to by the user, that is, the listening object sound, can only be heard by the user, the following masking technology is known: the listening object sound is output from the speaker to the first area where the user is located, and the masking sound that is a sound that hinders the hearing of the listening object sound is output from the speaker to the second area, such as the area where other people are located, which is the area where it is desired to suppress the hearing of the listening object sound (for example, patent documents 3 and 4).

[0004] Prior art literature:

[0005] Patent Literature:

[0006] Patent Document 1: Japanese Patent Application Publication No. 2006-74442

[0007] Patent Document 2: Japanese Patent Application Publication No. 2008-252625

[0008] Patent Document 3: Japanese Patent No. 6851980

[0009] Patent Document 4: Japanese Patent No. 5761259 Summary of the invention

[0010] Problems to be solved by the invention:

[0011] In reality, the above-mentioned local reproduction technology to which boundary sound field control is applied cannot completely eliminate the listening target sound propagating outside the first area, and it is difficult to completely eliminate the situation where the listening target sound leaks out of the first area and is heard.

[0012] Therefore, in the case where the listening target sound is a human voice that can be recognized by humans with high sensitivity, the content of the listening target sound may be recognized by others outside the first area.

[0013] On the other hand, according to the technology of outputting masking sound to the second area where hearing of the listening object sound is desired to be suppressed, thereby hindering hearing of the listening object sound in the second area, when the first area and the second area are relatively close spaces that are not isolated from each other, sometimes the masking sound prevents users in the first area from hearing the listening object sound well.

[0014] Therefore, the problem to be solved by the present invention is to control the sound field so that the user can hear the target sound, which is the sound to be heard, without difficulty and make it sufficiently difficult for others to hear the target sound.

[0015] Means used to solve the problem:

[0016] In order to achieve the above-mentioned problem, the present invention is a sound field control system, which uses a masking sound that masks the sound to be listened to by the user, i.e., the listening object sound, so that the listening object sound is difficult to be heard by others, wherein it comprises: a plurality of speakers; a first sound field control unit, which outputs the listening object sound from the plurality of speakers; and a second sound field control unit, which outputs the masking sound from the plurality of speakers. Here, the first sound field control unit outputs the listening object sound to the plurality of speakers in a manner that makes it partially reproduced in a closed space, and the closed space includes a listening range set as the range of the user's listening position for the listening object sound and the plurality of speakers. In addition, the second sound field control unit outputs the masking sound to the plurality of speakers in a manner that makes the sound pressure and sound pressure gradient of the masking sound as close to zero as possible on the following surface, and the surface is set to shield the main propagation path of the direct sound from the plurality of speakers to the listening range.

[0017] In addition, in order to achieve the above-mentioned problem, the present invention is a sound field control system that uses a masking sound that masks the sound to be listened to by the user, that is, the listening object sound, so that the listening object sound is difficult to be heard by others, wherein there are a plurality of groups consisting of speakers, a first filter, a second filter, and a mixer, wherein the first filter outputs the input listening object sound with a set transfer characteristic, the second filter outputs the input masking sound with a set transfer characteristic, and the mixer mixes the output of the first filter with the output of the second filter and outputs it to the speaker. Here, the first filter of each group is set with a transfer characteristic that makes the sound pressure and sound pressure gradient of the listening object sound as close to zero as possible at the boundary of a closed space, and the closed space includes a listening range set as the range of the listening position of the user for the listening object sound and the speakers of the plurality of groups. In addition, the second filter of each group is set with a transfer characteristic that makes the sound pressure and sound pressure gradient of the masking sound as close to zero as possible at the boundary of the space that includes the speakers of the plurality of groups but does not include the listening range and is close to the listening range.

[0018] Here, such a sound field control system may be such that the direction in front of a user listening to the object sound is set as the front, the loudspeakers of each group are arranged in front of the listening range, the space including the loudspeakers of the multiple groups but not including the listening range is set in front of the listening range, and for the second filter of each group, the following transfer characteristics are set, wherein the sound pressure and the sound pressure gradient of the masking sound are as close to zero as possible at the boundary on the rear side of the space which is the boundary on the listening range side, and the masking sound propagates toward the outside of the space through at least one of the front side and the left and right sides of the space.

[0019] In addition, in such a sound field control system, it is also possible to provide: a plurality of acoustic sensors; and a transfer characteristic setting unit, which estimates and sets the first filter and the second transfer characteristic of each group based on the output of the acoustic sensors in a state where the plurality of acoustic sensors are arranged at least at control points set on the boundary of the closed space and at control points set on the boundary of the space on the listening range side so that the responses of the listening object sound and the masking sound at each control point become target responses.

[0020] In such a sound field control system, a masking sound generating unit may be provided which generates the masking sound and adjusts the generated masking sound according to the listening target sound so that the masking sound is suitable for disturbing hearing of the listening target sound.

[0021] In addition, the present invention also provides a sound field control method, which uses a masking sound that masks the sound to be listened to by the user, i.e., the listening object sound, so that the listening object sound is difficult for others to hear. In the sound field control method, the listening object sound and the masking sound are output from a plurality of speakers, and the boundary sound field control of the listening object sound is performed in a manner that the sound pressure and the sound pressure gradient of the listening object sound are as close to zero as possible at the boundary of a closed space, wherein the closed space includes a listening range set as the range of the user's listening position for the listening object sound and the plurality of speakers, and the boundary sound field control of the masking sound is performed in a manner that the sound pressure and the sound pressure gradient of the masking sound are as close to zero as possible at the boundary of the space that includes the plurality of speakers but does not include the listening range and is close to the listening range.

[0022] According to the above-mentioned boundary sound field control system or boundary sound field control method, the masking sound is not propagated to the listening range for the user to listen to the listening object sound in the closed space where the listening object sound is partially reproduced, so the user can listen to the listening object sound well without being hindered by the masking sound. In addition, the area outside the closed space that is not close to the listening range side when observed from the speaker can be made into an area where the listening object sound does not leak out and the masking sound is propagated, so that it is difficult enough for others in the other area to listen to the listening object sound. In addition, the same speaker can be used when outputting the listening object sound and the masking sound, so that the user can listen to the listening object sound well and it is difficult for others to listen to the listening object sound as described above.

[0023] Effect of the invention:

[0024] As described above, according to the present invention, the sound field can be controlled so that the user can easily hear the target sound, which is the sound to be heard, and the target sound can be sufficiently difficult for others to hear. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a block diagram showing the configuration of a sound field control system according to an embodiment of the present invention.

[0026] Figure 2 It is a diagram showing an example of the boundary of controlling the sound pressure and the sound pressure gradient in the sound field control system according to the embodiment of the present invention.

[0027] Figure 3 It is a diagram showing an example of sound field control performed by the sound field control system according to the embodiment of the present invention.

[0028] Figure 4 It is a diagram showing another example of sound field control performed by the sound field control system according to the embodiment of the present invention.

[0029] Figure 5 It is a block diagram showing another configuration example of the sound field control system according to the embodiment of the present invention.

[0030] Description of reference numerals:

[0031] 1...speaker, 2...amplifier, 3...listening object sound filter group, 4...mixer unit, 5...masking sound generating unit, 6...masking sound filter group, 7...acoustic sensor, 8...filter characteristic setting unit, 31...first boundary sound field control filter, 41...mixer, 61...second boundary sound field control filter. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present invention will be described.

[0033] Figure 1 The configuration of a sound field control system according to this embodiment is shown.

[0034] The present sound field control system is a system for controlling the sound field so that a listening target sound, which is a predetermined sound, can be well heard only by the user and cannot be heard by other people.

[0035] As shown in the figure, the sound field control system includes a plurality of speakers 1 , amplifiers 2 corresponding to the speakers 1 , a listening sound filter group 3 , a mixer unit 4 , a masking sound generator 5 , and a masking sound filter group 6 .

[0036] The masking sound generation unit 5 generates a predetermined masking sound such as noise, and outputs the generated masking sound to the masking sound filter group 6 .

[0037] The listening target sound filter group 3 includes a plurality of first boundary sound field control filters 31 corresponding to the plurality of speakers on a one-to-one basis, and the listening target sound is input to each of the first boundary sound field control filters 31 .

[0038] The masking sound filter group 6 includes a plurality of second boundary sound field control filters 61 corresponding to the plurality of speakers on a one-to-one basis, and the masking sound generated by the masking sound generating unit 5 is input to each of the second boundary sound field control filters 61 .

[0039] The mixer unit 4 has mixers 41 corresponding to the plurality of speakers 1 on a one-to-one basis. Each mixer 41 mixes the output of the first boundary sound field control filter 31 of the corresponding speaker 1 which is the same as itself, with the output of the second boundary sound field control filter 61 of the corresponding speaker 1 which is the same as itself, and outputs the mixed output to the corresponding speaker 1 via the amplifier 2.

[0040] In such a configuration, each first boundary sound field control filter 31 is, for example, a FIR filter, and each of the first boundary sound field control filters 31 is preset with a filter coefficient (transfer characteristic) for performing a predetermined boundary sound field control on a listening target sound.

[0041] In addition, each second boundary sound field control filter 61 is, for example, an FIR filter, and a filter coefficient (transfer characteristic) for performing a predetermined boundary sound field control for a masking sound is preset for each filter.

[0042] Figure 2 ' a' and ' b' represent an example of boundary sound field control for the listening object sound implemented by each first boundary sound field control filter 31 of the listening object sound filter group 3, and an example of boundary sound field control for the masking sound implemented by each second boundary sound field control filter 61 of the masking sound filter group 6.

[0043] Figure 2 Examples a and b show a case where each part of the sound field control system except the speaker 1 is realized by software of a PC (personal computer).

[0044] This example shows a case where a user sitting on a chair in front of a desk is holding a remote conference via a PC placed on the desk, and speech sounds of other participants in the remote conference received by the PC become target sounds to be heard by the user.

[0045] In this example, a plurality of speakers 1 are arranged in front of and behind the PC.

[0046] As in Figure 2 a1 shows the situation viewed from the side and in Figure 2 As shown in a2 of FIG. 1 , the boundary sound field control for the listening object sound implemented by each first boundary sound field control filter 31 is a boundary sound field control that makes the sound pressure and the sound pressure gradient (sound pressure slope) as close to zero as possible at the boundary BA1 of the region A1 as a closed space, the closed space including the range UA assumed to be the moving range of the head of the user in the remote conference and each speaker 1. By performing such boundary sound field control, the listening object sound leaking to the outside of the boundary BA1 is minimized, and the listening object sound is locally reproduced in the region A1. In addition, making the sound pressure gradient (sound pressure slope) zero is equivalent to making the particle velocity zero.

[0047] Next, as in Figure 2 b1 shows the situation viewed from the side and in Figure 2 As shown in b2 when viewed from above, boundary sound field control for masking sound is performed by each second boundary sound field control filter 61 on the boundary of area A2 that does not include range UA assumed to be the movement range of the user's head but includes each speaker 1.

[0048] That is, boundary sound field control is performed in such a way that the sound pressure and sound pressure gradient (sound pressure slope) at the boundary of area A2 are as close to zero as possible at the boundary BA2U on the range UA side represented by the solid line, which is the main propagation path of direct sound from each speaker 1 to the range UA, and the masking sound is naturally radiated to the outside of area A2 through the boundary BA2N on the not range UA side represented by the dotted line.

[0049] By performing such boundary sound field control, the masking sound reaching the head of the user in the area UA from the boundary BA2U is minimized, and the masking sound reaches the direction not close to the area UA side with little change compared to the case where boundary sound field control of the masking sound is not performed.

[0050] By performing such boundary sound field control for the listening target sound and the boundary sound field control for the masking sound, as in Figure 3 A in FIG. 1 shows a situation viewed from the side and in FIG. Figure 3 As shown in FIG. 2 b when viewed from above, within the range UA in the area A1, which is assumed to be the moving range of the head of the user in the teleconference, only the listening target sound is transmitted from the speaker 1, and the masking sound hardly reaches.

[0051] Therefore, in a teleconference, the user can hear the target sound well without being disturbed by the masking sound.

[0052] On the other hand, the masking sound is transmitted toward the direction not close to the area UA side when viewed from each speaker 1, and the transmission of the listening target sound to the outside of the area A1 is minimized.

[0053] Therefore, the target sound hardly leaks out to other people outside the area A1 and in a direction not close to the range UA when viewed from the speaker 1 , and the leaked target sound is masked by the masking sound and prevented from being heard.

[0054] Furthermore, regarding the direction on the range UA side outside the area A1 as viewed from each speaker 1 , the target sound is hardly transmitted outside the area A1 , so that others in this direction can hardly hear the target sound.

[0055] Furthermore, when another person enters a range closer to each speaker 1 than the range UA in the area A1 where both the target sound and the masking sound are transmitted, the target sound is masked by the masking sound, making it difficult for the target sound to be heard.

[0056] An example of boundary sound field control performed by the sound field control system according to the present embodiment has been described above.

[0057] Here, in the above Figure 2 , Figure 3In the example shown, the various parts of the sound field control system except the speaker 1 are implemented by the software of the PC, but the built-in speaker of the PC can also be used as the speaker 1 of the sound field control system, and the sound field control system can also be separated from the PC and the PC can be used as the sound source device for listening to the object sound.

[0058] In the above example, the voices spoken by other participants in the remote conference are used as the listening target sounds, but any sounds may be used as the listening target sounds.

[0059] That is, for example, any sound such as broadcast sound from a radio or television broadcast, reproduced sound from an audio device, or answering sound from a telephone call may be used as the listening target sound.

[0060] In addition, about Figure 2 , Figure 3 The number or configuration of the speakers 1 in the example shown, or the boundaries BA1, BA2U, and BA2N can be arbitrary as long as the range UA assumed to be the movement range of the user's head is within a closed space surrounded by the boundary BA1 and the boundary BA2U blocks the main propagation path of direct sound from the speaker 1 to the range UA.

[0061] For example, Figure 4 As shown, multiple speakers 1 can also be configured to surround the user, and the boundary BA1 that makes the sound pressure and sound pressure gradient of the listening object sound as close to 0 as possible, and the boundary BA2U that makes the sound pressure and sound pressure gradient of the masking sound as close to 0 as possible, are set as boundaries with closed boundary surfaces, so that the inner side of the boundary BA1 includes each speaker 1 and the range UA, the inner side of the boundary BA1 and each speaker 1 includes the boundary BA2U, and the inner side of the boundary BA2U includes the range UA.

[0062] By setting the boundary BA1 and the boundary BA2U in this way, only the target sound is propagated in the range UA, so the user can hear the target sound well. In addition, only the masking sound is propagated outside the boundary BA1, so it can be made difficult for others outside the boundary BA1 to hear the target sound.

[0063] In addition, Figure 1 In the sound field control system shown, the masking sound generation unit 5 may generate a sound suitable for disturbing hearing of the listening target sound as a masking sound according to the listening target sound.

[0064] In this case, if Figure 5As shown, the listening object sound is also input to the masking sound generating unit 5, and in the masking sound generating unit 5, for example, the level of the generated masking sound is adjusted so that the ratio to the level of the listening object sound is fixed, or a sound having a frequency band overlapping with the listening object sound is generated in the masking sound generating unit 5 as the masking sound, or a sound having a frequency spectrum close to the listening object sound is generated in the masking sound generating unit 5 as the masking sound.

[0065] In addition, Figure 1 The sound field control system shown may also have a function of setting the filter coefficient (transfer characteristic) of the first boundary sound field control filter 31 of the listening sound filter group 3 or the second boundary sound field control filter 61 of the masking sound filter group 6 .

[0066] In this case, for example, Figure 5 As shown, in the sound field control system, a plurality of acoustic sensors 7 such as a microphone, a microphone array, a sound pressure sensor, or a sound pressure gradient sensor are provided, and a filter characteristic setting unit 8 is provided.

[0067] In addition, when the sound field control system is put into operation, the sound field control system or other equipment used in conjunction with the sound field control system is set up. Figure 2 The boundary of area A1 shown, i.e., the position on boundary BA1, the position on boundary BA2U of area A2 on the side of range UA, the position within range UA, or the position on the opposite side of range UA when viewed from boundary BA2U are used as control points, and each acoustic sensor 7 is arranged at each control point, and in the filter characteristic setting section 8, adjustment actions are performed in response to user instructions.

[0068] During the adjustment operation, the filter characteristic setting unit 8 obtains a transfer function from each speaker 1 to each control point based on the signal output to each speaker 1 and the output of each acoustic sensor 7, and calculates the filter coefficients of the first boundary sound field control filter 31 or the filter coefficients of the second boundary sound field control filter 61 for achieving the target response of the listening object sound and the masking sound at each control point based on the obtained transfer function, and sets them to the first boundary sound field control filter 31 or the second boundary sound field control filter 61.

[0069] Here, during the adjustment operation, a predetermined test signal may be output from the masking sound generating unit 5, and the listening sound filter group 3 and the masking sound filter group 6 may be controlled so as to sequentially output the test signal as is to each speaker 1, and in the filter characteristic setting unit 8, the test signal may be used as a signal output to each speaker 1 to obtain a transfer function from each speaker 1 to each control point.

[0070] In addition, regarding Figure 2In the case of the example of FIG. 1 , it is not necessary to strictly control the response of the masking sound on the boundary BA2N of the area A2 that is not on the side of the range UA, so the acoustic sensor 7 may not be arranged at the position on the boundary BA2N as a control point. For example, the control point may be set as the position on the opposite side of the range UA when viewed from the boundary BA2U, such as the center of the area A2 or the position on the opposite side of the range UA on the boundary BA1, and the target of the masking sound at the control point may be set to a response with sufficient sound pressure.

[0071] In addition, after the adjustment operation is completed, the acoustic sensor 7 is removed and the sound field control system is used.

[0072] The embodiments of the present invention have been described above.

[0073] As described above, according to the present embodiment, in the area including the listening position of the user, the user can hear the listening target sound well without being blocked by the masking sound, and the listening target sound does not leak to other areas, and the area where the masking sound is transmitted can make it difficult for others in the other areas to hear the listening target sound. In addition, the same speaker 1 can be used when outputting the listening target sound and the masking sound, so that the user can hear the listening target sound well and it is difficult for others to hear the listening target sound.

Claims

1. A sound field control system, which uses a masking sound to mask a sound to be heard by a user, i.e., a listening target sound, so that the listening target sound is difficult for others to hear, characterized in that: have: Multiple speakers; a first sound field control unit configured to output the listening target sound from the plurality of speakers; and The second sound field control unit outputs the masking sound from the plurality of speakers, the first sound field control unit outputs the listening target sound to the plurality of speakers in a manner such that the listening target sound is locally reproduced in a closed space, the closed space including a listening range set as a range of a listening position of the user for the listening target sound and the plurality of speakers, The second sound field control unit outputs the masking sound to the plurality of speakers so that the sound pressure and the sound pressure gradient of the masking sound are as close to zero as possible on a surface set to shield a main propagation path of direct sound from the plurality of speakers to the listening range.

2. A sound field control system that uses a masking sound to mask a sound that is a target sound for a user to hear, so that the target sound is difficult for others to hear, characterized in that: The sound field control system includes a plurality of groups consisting of a speaker, a first filter, a second filter, and a mixer, wherein the first filter outputs the input listening target sound with a set transfer characteristic, the second filter outputs the input masking sound with a set transfer characteristic, and the mixer mixes the output of the first filter and the output of the second filter and outputs them to the speaker, The first filter of each group is set to have a transfer characteristic such that the sound pressure and the sound pressure gradient of the listening target sound are as close to zero as possible at a boundary of a closed space, wherein the closed space includes a listening range set as a range of a listening position of the user for the listening target sound and the plurality of groups of speakers, The second filter of each group is set to have a transfer characteristic such that the sound pressure and the sound pressure gradient of the masking sound are as close to zero as possible at a boundary on the listening range side of a space including the plurality of groups of speakers but not including the listening range.

3. The sound field control system according to claim 2, characterized in that: The direction forward of a user listening to the target sound is defined as the front, and the speakers of each group are arranged in the front of the listening range. The space including the plurality of groups of speakers but not including the listening range is set in front of the listening range, The second filter of each group is set with the following transfer characteristics, which makes the sound pressure and sound pressure gradient of the masking sound as close to zero as possible at the boundary on the rear side of the space which is the boundary on the listening range side, and the masking sound propagates toward the outside of the space through at least one of the front side and left and right sides of the space.

4. The sound field control system according to any one of claims 2 to 4, characterized in that: have: multiple acoustic sensors; and A transfer characteristic setting unit estimates and sets the first filter and the second transfer characteristic of each group based on the output of the acoustic sensors in a state where the plurality of acoustic sensors are arranged at least at control points set on a boundary of the closed space and at control points set on a boundary of the space on the listening range side so that responses of the listening object sound and the masking sound at each control point become target responses.

5. The sound field control system according to any one of claims 2 to 4, characterized in that: The invention comprises a masking sound generating unit which generates the masking sound and adjusts the generated masking sound according to the listening target sound so that the masking sound is suitable for disturbing the listening of the listening target sound.

6. A sound field control method, using a masking sound for masking a sound to be heard by a user, i.e., a listening target sound, so that the listening target sound is difficult for others to hear, characterized in that: The target sound and the masking sound are output from a plurality of speakers, and performing boundary sound field control of the listening object sound in such a manner that the sound pressure and the sound pressure gradient of the listening object sound are as close to zero as possible at the boundary of a closed space, the closed space including a listening range set as a range of a listening position of the user for the listening object sound and the plurality of speakers, Boundary sound field control of the masking sound is performed so that the sound pressure and the sound pressure gradient of the masking sound are as close to zero as possible at a boundary on the listening range side of a space including the plurality of speakers but not including the listening range.

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