Sound field control system and sound field control method

Abstract

To provide a "sound field control system and sound field control method" that makes it difficult for others to hear sound to be heard.SOLUTION: An embodiment of the present invention performs: boundary sound field control of the sound corresponding to listening so that sound pressure and sound pressure gradient (sound pressure gradient) become zero as much as possible at the boundary BA1, which is the boundary between a range UA assumed as a moving range of a user's head and an area A1 in a closed space including a speaker 1 (a1, a2); and boundary sound field control of the masker sound so as to propagate outside through a boundary BA2N (dashed line) which is not on the UA side, so that the sound pressure and the sound pressure gradient (sound pressure gradient) become zero at the boundary BA2U (solid line) on the UA side among boundaries of an area A2 not including the range UA and including speaker 1 (b1, b2).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a technique for controlling a sound field so that a target sound that a user wishes to listen to can be heard only by that user. [Background technology]

[0002] As a technology for controlling a sound field so that the target sound, which is the sound that a user intends to hear, can only be heard by the user, a known local reproduction technology uses a boundary sound field control technology based on the Kirchhoff-Helmholtz integral equation to output the target sound from a speaker so that the sound pressure and sound pressure gradient of the target sound are zero at the boundary of a first area where the user is located, thereby minimizing the volume of the target sound that propagates outside the first area (for example, Patent Documents 1 and 2).

[0003] Furthermore, a known technique for controlling a sound field so that the target sound, which is the sound that a user wishes to hear, can only be heard by the user is a masking technique in which the target sound is output from a speaker in a first area where the user is located, while a masker sound, which is a sound that inhibits the hearing of the target sound, is output from a speaker in a second area, which is an area where it is desired to prevent the user from hearing the target sound, such as an area where others are located (for example, Patent Documents 3 and 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-74442 A [Patent Document 2] JP 2008-252625 A [Patent Document 3] Patent No. 6851980 [Patent Document 4] Patent No. 5761259 Summary of the Invention [Problem to be solved by the invention]

[0005] In reality, the local reproduction technology that applies the above-mentioned boundary sound field control cannot completely eliminate the sound to be listened to that propagates outside the first area, and it is difficult to completely prevent the sound to be listened to from leaking out and being heard outside the first area. For this reason, when the sound to be heard is a human voice to which humans have a high sensitivity and can recognize, the content of the sound to be heard may be recognized by other people outside the first area. On the other hand, according to a technology that prevents the target sound from being heard in a second area by outputting a masker sound to the second area where it is desired to prevent the target sound from being heard in the second area, if the first area and the second area are relatively close spaces that are not isolated from each other, the masker sound may prevent the user in the first area from hearing the target sound well.

[0006] Therefore, an object of the present invention is to control a sound field so that a user can easily hear a target sound, which is a sound to be heard, while making it sufficiently difficult for others to hear the target sound. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a sound field control system that uses a masker sound that masks a target sound to make it difficult for others to hear the target sound, which is a sound that a user is intended to hear, and includes a plurality of speakers, a first sound field control unit that outputs the target sound from the plurality of speakers, and a second sound field control unit that outputs the masker sound from the plurality of speakers. Here, the first sound field control unit outputs the target sound to the plurality of speakers so that the target sound is locally reproduced in a closed space including a listening range set as a range of the user's listening position for the target sound and the plurality of speakers. In addition, the second sound field control unit outputs the masker sound to the plurality of speakers so that the sound pressure and sound pressure gradient of the masker sound are as close to zero as possible on a surface set to block a main propagation path of direct sound from the plurality of speakers to the listening range.

[0008] In order to achieve the above object, the present invention provides a sound field control system that uses a masker sound to make it difficult for others to hear a target sound, which is a sound that a user is intended to hear, and includes a speaker, a first filter that outputs the input target sound with a set transfer characteristic, a second filter that outputs the input masker sound with a set transfer characteristic, and a mixer that mixes the output of the first filter and the output of the second filter and outputs the result to the speaker. Here, the first filter of each set has a transfer characteristic that makes the sound pressure and sound pressure gradient of the target sound as close to zero as possible at the boundary of a closed space including a listening range set as the range of the user's listening position for the target sound and the speakers of the multiple sets. Also, the second filter of each set has a transfer characteristic that makes the sound pressure and sound pressure gradient of the masker sound as close to zero as possible at the boundary of the listening range side of a space that includes the speakers of the multiple sets but does not include the listening range.

[0009] Here, such a sound field control system may position the speakers of each set in front of the listening range, with the direction that is in front of the user who hears the target sound being defined as "forward," set the space that includes the speakers of the multiple sets but does not include the listening range in front of the listening range, and set the second filter of each set to have transfer characteristics such that the sound pressure and sound pressure gradient of the masker sound are as close to zero as possible at the rear boundary, which is the boundary on the listening range side of the space, and the masker sound is propagated toward the outside of the space through at least one of the front and left / right boundaries of the space.

[0010] Furthermore, such a sound field control system may be provided with a plurality of acoustic sensors and a transfer characteristic setting unit that, with the plurality of acoustic sensors 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, calculates and sets a first filter and a second transfer characteristic of each set based on the output of the acoustic sensors so that the response at each control point of the sound to be listened to and the masker sound becomes a target response.

[0011] Furthermore, such a sound field control system may be provided with a masker sound generation unit that generates the masker sound and adjusts the generated masker sound according to the target sound so as to adapt it to interference with the audibility of the target sound. The present invention also provides a sound field control method for making it difficult for others to hear a target sound, which is a sound that a user is intended to hear, by using a masker sound that masks the target sound. This sound field control method outputs the target sound and the masker sound from multiple speakers, and performs boundary sound field control of the target sound so that the sound pressure and sound pressure gradient of the target sound are as close to zero as possible at the boundary of a closed space including a listening range set as a range of the user's listening position for the target sound and the multiple speakers, and performs boundary sound field control of the masker sound so that the sound pressure and sound pressure gradient of the masker sound are as close to zero as possible at the boundary of the listening range side of a space that includes the multiple speakers but does not include the listening range.

[0012] According to these boundary sound field control systems and boundary sound field control methods, the masker sound does not propagate to the listening range where the user hears the listening target sound in the closed space where the listening target sound is locally reproduced, so the user can hear the listening target sound well without being hindered by the masker sound. Also, an area that is not on the listening range side as seen from the speaker outside the closed space can be an area where the listening target sound does not leak out and the masker sound propagates, so it is possible to make it sufficiently difficult for others in the other area to hear the listening target sound. Also, by using the same speaker to output the listening target sound and the masker sound, it is possible to realize the above-mentioned improvement in the listening target sound for the user and the difficulty in hearing the listening target sound for others. Effect of the Invention

[0013] As described above, according to the present invention, it is possible to control a sound field so that a user can easily hear a target sound, which is a sound that is the target of listening, while making it sufficiently difficult for others to hear the target sound. [Brief description of the drawings]

[0014] [Figure 1] 1 is a block diagram showing a configuration of a sound field control system according to an embodiment of the present invention. [Diagram 2] 1A to 1C are diagrams illustrating examples of boundaries for controlling sound pressure and sound pressure gradient in a sound field control system according to an embodiment of the present invention. [Diagram 3] 1A to 1C are diagrams illustrating an example of sound field control by a sound field control system according to an embodiment of the present invention. [Figure 4] 11A to 11C are diagrams illustrating another example of sound field control by the sound field control system according to the embodiment of the present invention. [Diagram 5] FIG. 11 is a block diagram showing another example of the configuration of the sound field control system according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described. FIG. 1 shows the configuration of a sound field control system according to this embodiment. The present sound field control system is a system that controls a sound field so that a predetermined target sound can be heard clearly only by the user and is difficult for others to hear. As shown in the figure, the sound field control system includes a plurality of speakers 1, amplifiers 2 corresponding to each speaker 1, a group of target sound filters 3, a mixer unit 4, a masker sound generation unit 5, and a group of masker sound filters 6. The masker sound generation unit 5 generates a predetermined masker sound such as a noise sound, and outputs it to the masker sound filter group 6 . The audible sound filter group 3 includes a plurality of first boundary sound field control filters 31 in one-to-one correspondence with the plurality of speakers, and each of the first boundary sound field control filters 31 receives an audible sound as input. The masker sound filter group 6 includes a plurality of second boundary sound field control filters 61 each having a one-to-one correspondence with a plurality of speakers, and the masker sound generated by the masker sound generation unit 5 is input to each of the second boundary sound field control filters 61. The mixer unit 4 has mixers 41 that correspond one-to-one to the multiple speakers, and each mixer 41 mixes the output of the first boundary sound field control filter 31 that is the same as the corresponding speaker 1 and the output of the second boundary sound field control filter 61 that is the same as the corresponding speaker 1, and outputs the result to the corresponding speaker 1 via the amplifier 2.

[0016] In such a configuration, each of the first boundary sound field control filters 31 is, for example, an FIR filter, and a filter coefficient (transmission characteristic) for performing a predetermined boundary sound field control on audible sounds is set in advance for each of them. Moreover, each of the second boundary sound field control filters 61 is, for example, an FIR filter, and a filter coefficient (transmission characteristic) for performing a predetermined boundary sound field control on the masker sound is set in advance for each of them. 2a and 2b show an example of boundary sound field control for audible sounds realized by each first boundary sound field control filter 31 of the audible sound filter group 3, and an example of boundary sound field control for masker sounds realized by each second boundary sound field control filter 61 of the masker sound filter group 6. The examples of Figures 2a and 2b show a case where each part of the sound field control system except for the speaker 1 is realized by software of a PC (personal computer). This example also shows a case where a user sitting in a chair at the front of a desk holds a remote conference via a PC placed on the desk, and the speech of other participants in the remote conference received by the PC becomes the sound that the user hears. In this example, a number of speakers 1 are arranged in front of and behind the PC. As shown in Fig. 2a1 as viewed from the side and in Fig. 2a2 as viewed from above, the boundary sound field control for audible sound realized by each first boundary sound field control filter 31 is a boundary sound field control that makes the sound pressure and sound pressure gradient (sound pressure gradient) as close to zero as possible at the boundary BA1, which is the boundary between the range UA assumed to be the range of movement of the user's head during a remote conference and the area A1, which is a closed space including each speaker 1. By performing such boundary sound field control, the audible sound leaking outside the boundary BA1 is minimized, and the audible sound is locally reproduced within the area A1. Note that making the sound pressure gradient (sound pressure gradient) zero is equivalent to making the particle velocity zero.

[0017] Next, as shown in Figure 2b1 as viewed from the side and in Figure 2b2 as viewed from above, the boundary sound field control for masker sounds realized by each second boundary sound field control filter 61 is performed on the boundary of area A2 including each speaker 1, excluding range UA expected as the range of movement of the user's head.

[0018] In other words, boundary sound field control is performed so that the sound pressure and sound pressure gradient (sound pressure gradient) are as close to zero as possible at boundary BA2U on the range UA side shown by a solid line, which blocks the main propagation path of direct sound from each speaker 1 to range UA, among the boundaries of area A2, and so that the masker sound is naturally radiated outside area A2 through boundary BA2N, which is not on the range UA side shown by a dashed line.

[0019] By performing such boundary sound field control, the masker sound that reaches the user's head located within the range UA from the boundary BA2U is minimized, and the masker sound reaches directions that are not on the range UA side without much change compared to when boundary sound field control of the masker sound is not performed. By performing such boundary sound field control for audible sounds and boundary sound field control for masker sounds, only the sounds to be heard are transmitted from speaker 1 to range UA, which is expected to be the range over which a user's head will move during a remote conference in area A1, and almost no masker sounds reach that range, as shown in Figure 3a when viewed from the side and in Figure 3b when viewed from above.

[0020] Therefore, during a remote conference, the user can clearly hear the target sound without being disturbed by the masker sound. On the other hand, masker sounds are transmitted in directions not on the range UA side as seen from each speaker 1, and transmission of the target sound to the outside of area A1 is minimized. Therefore, almost no sound to be heard leaks out to others in a direction that is not on the range UA side as viewed from speaker 1 outside area A1, and even the sound to be heard that does leak out is masked by the masker sound, making it difficult for the person to hear it. In addition, in the direction toward the range UA as seen from each speaker 1 outside the area A1, the sound to be listened to is hardly transmitted outside the area A1, making it difficult for others in that direction to hear the sound to be listened to. Furthermore, if another person enters the range within area A1 on the speaker 1 side of range UA where both the sound to be listened to and the masker sound are transmitted, the sound to be listened to will be masked by the masker sound, making it difficult to hear the sound to be listened to. An example of the boundary sound field control performed by the sound field control system of this embodiment has been described above. In the examples shown in Figures 2 and 3 above, each part of the sound field control system except for speaker 1 is realized by PC software, but the PC's built-in speaker may be used as speaker 1 of the sound field control system, or the sound field control system may be provided separately from the PC, and the PC may be used as the sound source device for the sound to be listened to.

[0021] In the above example, the sound to be listened to is the voice of another participant in the remote conference, but any sound may be the sound to be listened to. That is, the target sound may be any sound, such as the broadcast sound of a radio or television broadcast, the sound reproduced by an audio device, or the sound of an incoming telephone call. In addition, the number and arrangement of speakers 1 in the examples shown in Figures 2 and 3, as well as boundaries BA1, BA2U, and BA2N, may be arbitrary so long as the range UA expected as the range of movement of the user's head is within a closed space surrounded by boundary BA1, and boundary BA2U is arranged so as to block the main propagation path of direct sound from speaker 1 to range UA.

[0022] For example, as shown in Figure 4, multiple speakers 1 may be arranged to surround the user, and a boundary BA1 that reduces the sound pressure and sound pressure gradient of the sound to be listened to as close to zero as possible and a boundary BA2U that reduces the sound pressure and sound pressure gradient of the masker sound as close to zero as possible may be set as closed boundaries, with each speaker 1 and range UA included inside boundary BA1, boundary BA2U included inside boundary BA1 and each speaker 1, and range UA included inside boundary BA2U. Even if the boundaries BA1 and BA2U are set in this way, only the target sound propagates within the range UA, so the user can hear the target sound well. Also, only the masker sound propagates outside the boundary BA1, so it is sufficiently difficult for others outside the boundary BA1 to hear the target sound.

[0023] In the sound field control system shown in FIG. 1, the masker sound generating unit 5 may generate, as a masker sound, a sound that is suitable for interfering with the audibility of the target sound, in accordance with the target sound. In this case, as shown in FIG. 5, the sound to be listened to is also input to the masker sound generation unit 5, and the masker sound generation unit 5 adjusts the level of the masker sound to be generated so that the level ratio with the sound to be listened to is constant, or generates as the masker sound a sound whose frequency band overlaps with the sound to be listened to, or generates as the masker sound a sound whose frequency spectrum is close to that of the sound to be listened to.

[0024] In addition, the sound field control system shown in FIG. 1 may be provided with a function for setting the filter coefficients (transmission characteristics) of the first boundary sound field control filter 31 of the audible sound filter group 3 and the second boundary sound field control filter 61 of the masker sound filter group 6. In this case, for example, as shown in FIG. 5, the sound field control system is provided with a plurality of acoustic sensors 7 such as microphones, microphone arrays, sound pressure sensors, and sound pressure gradient sensors, and is also provided with a filter characteristic setting unit 8. Then, when the sound field control system is started up, with the sound field control system and other equipment to be used with the sound field control system set up, the positions on boundary BA1 which is the boundary of area A1 shown in FIG. 2, the positions on boundary BA2U on the range UA side of area A2, the positions within range UA, and the positions on the opposite side of range UA as viewed from boundary BA2U are set as control points, and each acoustic sensor 7 is placed at each control point, and the filter characteristic setting unit 8 performs an adjustment operation in response to user instructions.

[0025] In the adjustment operation, the filter characteristic setting unit 8 calculates 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 from the calculated transfer function, calculates the filter coefficients of the first boundary sound field control filter 31 and the second boundary sound field control filter 61 that realize the target responses of the sound to be listened to and the masker sound at each control point, and sets them in the first boundary sound field control filter 31 and the second boundary sound field control filter 61.

[0026] In the adjustment operation, a predetermined test signal is output from the masker sound generation unit 5, and this test signal is output sequentially to each speaker 1 by controlling the audible sound filter group 3 and the masker sound filter group 6, and the filter characteristic setting unit 8 may obtain a transfer function from each speaker 1 to each control point using this test signal as the signal output to each speaker 1.

[0027] 2, for the boundary BA2N that is not on the range UA side of the area A2, it is not necessary to strictly control the response of the masker sound on the boundary, so it is not necessary to place the acoustic sensor 7 at a position on the boundary BA2N as a control point. For example, a control point may be set as a position on the opposite side of the range UA as seen from the boundary BA2U, such as the center position of the area A2 or a position on the opposite side of the range UA on the boundary BA1, and the target of the masker sound at this control point may be a response with sufficient sound pressure.

[0028] After the adjustment operation is completed, the acoustic sensor 7 is removed and the sound field control system is used. The embodiment of the present invention has been described above. As described above, according to this embodiment, the target sound can be satisfactorily heard in an area including the user's listening position without being disturbed by the masker sound, while the target sound does not leak out of most other areas, and the masker sound is transmitted to the other areas, making it sufficiently difficult for others in those other areas to hear the target sound. Also, by using the same speaker 1 to output the target sound and the masker sound, the target sound can be satisfactorily heard by the user, while making it sufficiently difficult for others to hear the target sound. [Explanation of symbols]

[0029] 1...speaker, 2...amplifier, 3...group of target sound filters, 4...mixer section, 5...masker sound generation section, 6...group of masker sound filters, 7...acoustic sensor, 8...filter characteristic setting section, 31...first boundary sound field control filter, 41...mixer, 61...second boundary sound field control filter.

Claims

1. A sound field control system that uses a masker sound that masks a target sound that a user wants to hear to make it difficult for others to hear the target sound, A plurality of speakers; a first sound field control unit that outputs the target sound from the plurality of speakers; a second sound field control unit that outputs the masker sound from the plurality of speakers, The first sound field control unit outputs the target sound to the plurality of speakers so that the target sound is locally reproduced in a closed space including a listening range set as a range of a listening position of the user for the target sound and the plurality of speakers; The second sound field control unit outputs the masker sound to the multiple speakers so that the sound pressure and sound pressure gradient of the masker sound are as close to zero as possible on a surface configured to block the main propagation path of direct sound from the multiple speakers to the listening range.

2. A sound field control system that uses a masker sound that masks a target sound that a user wants to hear to make it difficult for others to hear the target sound, a plurality of sets of a speaker, a first filter that outputs the input target sound with a set transfer characteristic, a second filter that outputs the input masker sound with a set transfer characteristic, and a mixer that mixes the output of the first filter and the output of the second filter and outputs the result to the speaker; A transfer characteristic is set for the first filter of each set such that the sound pressure and sound pressure gradient of the target sound are as close to zero as possible at a boundary between a listening range set as a range of a listening position of the target sound of the user and the plurality of sets of speakers and a closed space including the listening range and the plurality of sets of speakers; A sound field control system characterized in that the second filter of each set has a transfer characteristic that makes the sound pressure and sound pressure gradient of the masker sound as close to zero as possible at the boundary on the listening range side of a space that includes the speakers of the multiple sets but does not include the listening range.

3. 3. The sound field control system according to claim 2, The speaker of each set is disposed in front of the listening range, with the direction in front of a user who listens to the target sound being defined as the front; the space including the plurality of sets of speakers but not including the listening range is set in front of the listening range, A sound field control system characterized in that the second filter of each set has a transfer characteristic such that the sound pressure and sound pressure gradient of the masker sound are as close to zero as possible at the rear boundary, which is the boundary on the listening range side of the space, and the masker sound is propagated toward the outside of the space through at least one of the front and left / right boundaries of the space.

4. 5. A sound field control system according to claim 2, 3 or 4, A plurality of acoustic sensors; A sound field control system comprising: a transfer characteristic setting unit that calculates and sets a first filter and a second transfer characteristic of each set based on the output of the acoustic sensors, in a state in which the plurality of acoustic sensors are disposed at least at a control point set on the boundary of the closed space and a control point set on the boundary of the space on the listening range side, so that the response at each control point of the target sound and the masker sound becomes a target response based on the output of the acoustic sensors.

5. 5. A sound field control system according to claim 2, 3 or 4, A sound field control system comprising: a masker sound generation unit that generates the masker sound and adjusts the generated masker sound according to the target sound so as to conform to interference with the audibility of the target sound.

6. A sound field control method for making it difficult for others to hear a target sound, which is a sound that a user is intended to hear, by using a masker sound that masks the target sound, comprising: The target sound and the masker sound are output from a plurality of speakers, A boundary sound field control is performed on the sound to be listened to such that the sound pressure and sound pressure gradient of the sound to be listened to are as close to zero as possible at a boundary between a listening range set as a range of a listening position of the sound to be listened to by the user and a closed space including the plurality of speakers; A sound field control method comprising the steps of: performing boundary sound field control of the masker sound so that the sound pressure and sound pressure gradient of the masker sound are as close to zero as possible at the boundary on the listening range side of a space that includes the multiple speakers but does not include the listening range.

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