Audio system

Abstract

To provide an audio system that outputs sound of a sound source which is different for each user toward a plurality of users and suitably reduces leakage of the sound outputted to the other users.SOLUTION: A sound X1(f) outputted by an i-th audio source apparatus ASi is adjusted by an i-th noise reduction filter Wi with a frequency transfer function Wii(f) that is set to the noise reduction filter Wi and outputted from an i-th speaker SPKi. What is set to the noise reduction filter Wi, where m=integer from 1 to n, except i, is a frequency transfer function Wii(f) that reduces sound for a frequency at which a gain of a frequency transfer function Cim(f) from the SPKi to a user Pm is relatively larger than a gain of a frequency transfer function Cii(f) from the SPKi to a user Pi and increases sound for a frequency at which the gain of the Cim(f) is relatively smaller than the gain of the Cii(f).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an audio system that outputs sounds from different sound sources to a plurality of users. [Background technology]

[0002] As an audio system that outputs sound from a different sound source to multiple users, there is known an audio system that outputs sound from a different sound source to each user seated in a different seat of a car (for example, Patent Document 1).

[0003] In such an audio system that outputs sounds from different sound sources to a plurality of users, the sounds heard by each user and outputted to other users become noise.

[0004] Known technologies for reducing sounds that are output to other users and that can be heard by each user include a technology that controls the directionality of the sound output to a user so that the sound does not reach other users, and an active noise control technology that outputs a sound that cancels out the noise from a speaker (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-12917 A Summary of the Invention [Problem to be solved by the invention]

[0006] In an audio system that outputs sound from different sound sources to multiple users, when the sound output to other users that can be heard by each user is reduced by controlling the directionality as described above, a good effect can be obtained in the high frequency range (5 kHz or higher), but it is difficult to obtain a sufficient effect in the frequency range where the human ear is most sensitive (around 2 to 4 kHz).

[0007] Furthermore, with the above-mentioned active noise control, it is difficult to widen the range in which high-frequency noise can be reduced, and it is difficult to obtain a sufficient effect.

[0008] Therefore, an object of the present invention is to effectively reduce sounds output to other users that are heard by each user in an audio system that outputs sounds from different sound sources to multiple users. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides an audio system that outputs sounds of different sound sources for each user to n users from 1st to nth (n>2), the audio system including n sound source devices from 1st to nth, n speakers from 1st to nth, and n filters. The i-th filter (where i is an integer from 1 to n) transmits the sound output by the i-th sound source device to the i-th speaker with a set frequency transfer characteristic. The frequency transfer characteristic set in the i-th filter is a frequency transfer function that reduces the sound at a frequency where the ratio of the gain of the frequency transfer function from the i-th speaker to the m-th user to the gain of the frequency transfer function from the i-th speaker to the i-th user tends to be relatively large, and increases the sound at a frequency where the ratio of the gain of the frequency transfer function from the i-th speaker to the m-th user to the gain of the frequency transfer function from the i-th speaker to the i-th user tends to be relatively small, where m is an integer from 1 to n excluding i.

[0010] Here, the frequency transfer function from the i-th speaker to the i-th user in this audio system is Cii (f), C ii The complex conjugate of (f) is C * ii (f) The frequency transfer function from the i-th speaker to the m-th user is C im (f), C im The complex conjugate of (f) is C * im (f) is the frequency transfer characteristic W set for the i-th filter. ii of,

[0011]

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[0012] In addition, this audio system may be configured such that an adaptive filter, which receives as input the sound output by the i-th sound source device and whose output is input to the i-th speaker, performs an adaptive operation in which the difference between the sound obtained by applying a frequency transfer function to the sound output by the i-th sound source device that is the same as the frequency transfer function from the i-th speaker to the i-th user and the output of the microphone placed at the i-th user's sound listening position, and the output of the microphone placed at the m-th user's sound listening position, are set as the frequency transfer characteristic of the i-th filter.

[0013] Alternatively, this audio system may be configured such that an adaptive filter, which receives as input the sound output by the ith sound source device and whose output is input to the ith speaker, performs an adaptive operation in which the difference between the sound output by the ith sound source device and the output of a microphone placed at the sound listening position of the ith user, weighted with a predetermined weight, is set as the frequency transfer characteristic of the ith filter. The frequency transfer characteristic of the adaptive filter is set as the frequency transfer characteristic of the ith filter.

[0014] To achieve the above object, the present invention provides an audio system that outputs sounds from different sound sources to n users, numbered 1 to n (n>2), comprising n sound source devices numbered 1 to n, n speakers numbered 1 to n, and n filters. The i-th filter (where i is an integer number ranging from 1 to n) transmits the sound output by the i-th sound source device to the i-th speaker with a set frequency transmission characteristic. Furthermore, the frequency transfer characteristic set in the i-th filter, with a user other than the i-th user for whom the ratio of the gain of the frequency transfer function from the i-th speaker to the i-th user is the largest, is a frequency transfer function that reduces the sound at frequencies where the ratio of the gain of the frequency transfer function from the i-th speaker to the i-th user is relatively large, and increases the sound at frequencies where the ratio of the gain of the frequency transfer function from the i-th speaker to the i-th user is relatively small.

[0015] Here, in this audio system, the frequency transfer function from the i-th speaker to the i-th user is C ii (f), C ii The complex conjugate of (f) is C * ii (f), the user of interest is the d-th user, and the frequency transfer function from the i-th speaker to the d-th user is C id (f), C id The complex conjugate of (f) is C * id (f) is the frequency transfer characteristic W set for the i-th filter. ii teeth,

[0016]

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[0017] In addition, this audio system may be configured such that an adaptive filter, which receives as input the sound output by the i-th sound source device and whose output is input to the i-th speaker, performs an adaptive operation in which the difference between the sound obtained by applying a frequency transfer function to the sound output by the i-th sound source device that is the same as the frequency transfer function from the i-th speaker to the i-th user and the output of the microphone placed at the sound listening position of the i-th user, and the output of the microphone placed at the sound listening position of the target user, are set as the frequency transfer characteristic of the i-th filter. Here, in the above audio system, each of the filters may be a graphic equalizer.

[0018] According to the audio system described above, it is possible to suppress the output sound of the i-th speaker that is overheard by users other than the i-th user, while minimizing the reduction in the volume and auditory quality of the output sound of the i-th speaker that can be heard by the i-th user. Effect of the Invention

[0019] As described above, according to the present invention, in an audio system that outputs sound from different sound sources to multiple users, the sound output to other users that is heard by each user can be effectively reduced. [Brief description of the drawings]

[0020] [Figure 1] 1 is a block diagram showing a configuration of an audio system according to an embodiment of the present invention. [Diagram 2] 1 is a diagram illustrating an application example of an audio system according to an embodiment of the present invention. [Diagram 3] FIG. 4 is a diagram showing a configuration for learning a transfer function of a noise reduction filter according to an embodiment of the present invention. [Figure 4] FIG. 11 is a diagram showing another configuration for learning the transfer function of the noise reduction filter according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described. FIG. 1 shows the configuration of an audio system according to this embodiment.

[0022] The illustrated audio system is an audio system that outputs sound from a different sound source for each user to n (n≧2) users, P1 to Pn, and is equipped with n audio source devices, AS1 to ASn, n noise reduction filters, W1 to Wn, and n speakers, SPK1 to SPKn.

[0023] The i-th audio source device ASi (i is an integer from 1 to n) is a device that outputs a sound to be heard by the i-th user Pi, and the sound Xi(f) output from the i-th audio source device ASi is converted into a frequency transfer function W ii The signal is adjusted in (f) and output from the i-th speaker SPKi.

[0024] That is, for example, the second audio source device AS2 is a device that outputs a sound listened to by the second user P2, and the sound X2(f) outputted from the second audio source device AS2 is converted by the second noise reduction filter W2 into a frequency transfer function W 22 It is adjusted in (f) and output from the second speaker SPK2.

[0025] The audio system is a system that outputs sound from different audio source devices ASi to users Pi seated in each seat of a car, as shown in FIG. 2, for example, and the i-th speaker SPKi is positioned, for example, near the i-th seat PSi so as to radiate sound toward the user Pi seated in the i-th seat PSi.

[0026] That is, for example, the second speaker SPK2 is disposed near the second seat PS2 so as to radiate sound toward the user P2 seated in the second seat PS2.

[0027] Returning to Figure 1, let j be an integer between 1 and n. ij (f) represents the frequency transfer function of the sound output from the i-th speaker SPKi to the j-th user Pj, and is a complex number whose value changes depending on the frequency f.

[0028] For example, C 11 (f) represents the frequency transfer function of the sound output from the first speaker SPK1 to the first user P1, and C 12 (f) represents the frequency transfer function of the sound output from the first speaker SPK1 to the second user P2.

[0029] Next, the noise reduction filter Wi is defined as C ii (f) Gain vs. C im At frequencies where the gain ratio of (f) tends to be relatively large, the sound is reduced, and C ii (f) Gain vs. C im The frequency transfer function W (f) makes the sound louder at frequencies where the gain ratio tends to be relatively small. ii (f) is set, and the sound Xi(f) output from the i-th audio source device ASi is converted into a frequency transfer function W ii The signal is adjusted in (f) and output from the i-th speaker SPKi.

[0030] More specifically, C ii (f) Gain vs. C im Based on Equation 1, which shows the tendency of the gain of (f), the frequency transfer function W ii (f) is calculated in advance, and the noise reduction filter W ii Set to (f), where X *Let denote the complex conjugate of X.

[0031]

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[0032] As a result, when the audio Xi(f) output from the i-th audio source device ASi is output directly from the i-th speaker SPKi without providing a noise reduction filter Wi, users Pm other than the i-th user Pi can hear it, and sounds with relatively high frequencies at which the output sound from the speaker SPKi is suppressed by the noise reduction filter Wi and output from the speaker SPKi, and when the audio Xi(f) output from the i-th audio source device ASi is output directly from the i-th speaker SPKi without providing a noise reduction filter Wi, users Pm other than the i-th user Pi can hear it, and sounds with relatively low frequencies at which the output sound from the speaker SPKi is emphasized by the noise reduction filter Wi(f) and output from the speaker SPKi.

[0033] Therefore, by providing a noise reduction filter Wi, the output sound of the speaker SPKi that reaches users Pm other than the i-th user Pi becomes relatively small, so that the output sound of the speaker SPKi that leaks out and is heard by users Pm other than the i-th user Pi can be reduced without reducing the volume or auditory quality of the output sound of the speaker SPKi that can be heard by the i-th user Pi.

[0034] For example, the first noise reduction filter W1 has a filter C 11 Compared to the gain of (f), C calculated by Eq. 1m At frequencies where the gain of (f) tends to be large, the volume is reduced, and C 11 Compared to the gain of (f), C calculated by Eq. 1m The frequency transfer function W (f) makes the sound louder at frequencies where the gain tends to be small. 11 (f) is set, and the sound X1(f) output from the first audio source device AS1 is converted into a frequency transfer function W 11It is adjusted in (f) and output from the first speaker SPK1.

[0035] As a result, compared to when the noise reduction filter W1 is not provided, the output sound of the speaker SPK1 that reaches users Pm other than the first user P1 becomes relatively small, and the output sound of the speaker SPK1 that leaks out and is heard by users Pm other than the first user P1 can be reduced without reducing as much as possible the volume and auditory quality of the output sound of the speaker SPK1 that can be heard by the first user P1. Next, the frequency transfer function W ii The operation of calculating (f) will now be described.

[0036] In the following, the frequency transfer function W1 set in the noise reduction filter W1 is 11 Taking the calculation of (f) as an example, the frequency transfer function W ii The operation of calculating (f) will now be described. Frequency transfer function W 11 The calculation of (f) is carried out in advance in the configuration shown in FIG.

[0037] As shown in the figure, this configuration includes an audio source device AS1, a target setting section 301, an adaptive filter 302, a speaker SPK1, n microphones MC1 to MCn, and n subtractors AD1 to ADn. The i-th microphone MCi is placed at the sound listening position of the i-th user Pi.

[0038] The target setting unit 301 includes n filters 3011 that receive the output X1(f) of the audio source device AS1 as an input. The i-th filter 3011 has a frequency transfer function H 1i (f) is set.

[0039] The adaptive filter 302 includes a variable filter 3021 that receives the output X1(f) of the audio source device AS1 as an input, and an adaptive algorithm execution unit 3022, and the output of the variable filter 3021 is output from the speaker SPK1.

[0040] The i-th adder ADi calculates the frequency transfer function H 1i (f) is the output D of the i-th filter 3011 i (f) to the output Y of the i-th microphone MCi i (f) is subtracted and the error E between the i i The signal (f) is output to the adaptive filter 302.

[0041] The adaptive algorithm execution unit 3022 of the adaptive filter 302 executes a predetermined adaptive algorithm such as Multiple Error Filtered-X LMS (MEFX LMS), and performs an adaptive operation to update the frequency transfer characteristic G11(f) of the variable filter 3021 so that the sum of the individual powers of the n error signals output from the n computing units AD1-ADn, i.e., error signal E1(f) to error signal En(f), is minimized.

[0042] In this configuration, the audio source device AS1 is caused to output X1(f) while the adaptive algorithm execution unit 3022 is caused to perform an adaptive operation, and the frequency transfer characteristic G 11 If converged, the converged frequency transfer characteristic G 11 The frequency transfer function W 11 (f).

[0043] Here, the frequency transfer function C from the actual speaker SPK1 to the first user P1 11 (f) is the frequency transfer function from the target speaker SPK1 to the first user P1, and the frequency transfer function C 11 (f) is the frequency transfer function H 11 (f). In addition, m may be an integer between 2 and n, and the frequency transfer function from the target speaker SPKm to the m-th user Pm may be a frequency transfer function with a gain of 0 for all frequencies, and the frequency transfer function H 1m may be set to have zero gain for all frequencies. Thus, the frequency transfer function C 11 (f) is the frequency transfer function H 11 (f), and the frequency transfer function H 1m When the gain is set to 0 for all frequencies, the calculated frequency transfer function W 11 (f) is expressed as equation 2.

[0044]

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[0045] In addition, the frequency transfer function H 11 (f) The frequency transfer function C from the actual speaker SPK1 to the first user P1 11 (f) may be pre-tuned. The above is the frequency transfer function W1 set for the first noise reduction filter W1. 11 The calculation of (f) was explained.

[0046] Here, the frequency transfer function W set for an arbitrary noise reduction filter Wi is ii (f) can also be calculated in the same way by changing the order so that the i-th is the first and applying the above configuration and operation. The frequency transfer function W ii If equation (f) is expressed in terms of i, it becomes equation 3.

[0047]

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[0048] By the way, the frequency transfer function W of the first noise reduction filter W1 as described above is 11 As shown in FIG. 4, the calculation of (f) is performed by providing multipliers MP1 to MPn, and multiplying the error E i (f) may be multiplied by a weight Ki and output to the adaptive filter 302.

[0049] In this case, C1m * (f) C1m(f) / C11 * (f) Let m be the value at which C11(f) is maximized, and let d be the error E d The weight Ki of the error i(f) other than (f) and error E1(f) may be set to 0. In this case, the error E d The weights Kd and K1 of (f) and error E1(f) can be set to 1. In this case, the calculated frequency transfer function W 11 (f) is expressed as Equation 4.

[0050]

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[0051] By doing so, it is possible to most effectively reduce the output sound of the speaker SPK1 heard by the user Pd, who is the one who hears the loudest output sound of the speaker SPK1. 11 The amount of processing required for the adaptive operation of the adaptive algorithm execution unit 3022 to calculate (f) can also be reduced.

[0052] Here, for any noise reduction filter Wi, we also * (f) Cim(f) / Cii * (f) Let m be the value at which ii(f) is maximized, and let d be the error E d (f) and the error Ei(f) other than the weight Km of the error Em(f) is set to 0, and the error E d The weights Kd and Ki of (f) and the error Ei(f) may be set to 1. In this case, the frequency transfer function W ii The equation for (f) becomes Equation 5.

[0053]

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[0054] Here, since the function of the noise reduction filter Wi in the above embodiment is to adjust the gain for each frequency of the audio Xi(f) output from the i-th audio source device ASi, the noise reduction filter Wi may be a graphic equalizer that adjusts the gain for each frequency band, such as for each 1 / 3 octave band. [Explanation of symbols]

[0055] AS1-ASn...audio source devices, AD1-ADn...subtractors, MC1-MCn...microphones, MP1-MPn...multipliers, P1-Pn...users, SPK1-SPK...speakers, W1-Wn...noise reduction filters, 301...target setting unit, 302...adaptive filter, 3011...filter, 3021...variable filter, 3022...adaptive algorithm execution unit.

Claims

1. An audio system that outputs sounds of different sound sources to n users, from 1st to nth (n>2), n sound source devices numbered 1 to n; n speakers numbered 1 to n; n filters; The i-th filter (where i is an integer from 1 to n) transmits the sound output by the i-th sound source device to the i-th speaker with a set frequency transmission characteristic, An audio system characterized in that the frequency transfer characteristic set for the i-th filter is a frequency transfer function that reduces the sound at frequencies where the ratio of the gain of the frequency transfer function from the i-th speaker to the m-th user to the gain of the frequency transfer function from the i-th speaker to the i-th user tends to be relatively large, and that increases the sound at frequencies where the ratio of the gain of the frequency transfer function from the i-th speaker to the m-th user to the gain of the frequency transfer function from the i-th speaker to the i-th user tends to be relatively small, where m is an integer from 1 to n excluding i.

2. An audio system that outputs sounds of different sound sources to n users, from 1st to nth (n>2), n sound source devices numbered 1 to n; n speakers numbered 1 to n; n filters; The i-th filter (where i is an integer from 1 to n) transmits the sound output by the i-th sound source device to the i-th speaker with a set frequency transmission characteristic, An audio system characterized in that a user other than the i-th user for whom the ratio of the gain of the frequency transfer function from the i-th speaker to the i-th user is the largest to the gain of the frequency transfer function from the i-th speaker to the i-th user is taken as a user of interest, and the frequency transfer characteristic set in the i-th filter is a frequency transfer function that reduces the sound at frequencies for which the ratio of the gain of the frequency transfer function from the i-th speaker to the user of interest to the gain of the frequency transfer function from the i-th speaker to the i-th user is relatively large, and increases the sound at frequencies for which the ratio of the gain of the frequency transfer function from the i-th speaker to the user of interest to the gain of the frequency transfer function from the i-th speaker to the i-th user is relatively small.

3. 2. The audio system of claim 1, The frequency transfer function from the i-th speaker to the i-th user is C ii (f), C ii The complex conjugate of (f) is C ＊ ii (f) The frequency transfer function from the i-th speaker to the m-th user is C im (f), C im The complex conjugate of (f) is C ＊ im (f) is the frequency transfer characteristic W set for the i-th filter. ii teeth, [0010] 1. An audio system comprising:

4. 3. The audio system of claim 2, The frequency transfer function from the i-th speaker to the i-th user is C ii (f), C ii The complex conjugate of (f) is C ＊ ii (f), the user of interest is the d-th user, and the frequency transfer function from the i-th speaker to the d-th user is C id (f), C id The complex conjugate of (f) is C ＊ id (f) is the frequency transfer characteristic W set for the i-th filter. ii teeth, [0025] 1. An audio system comprising:

5. 2. The audio system of claim 1, An audio system characterized in that an adaptive filter, which receives as input the sound output by the i-th sound source device and whose output is the input to the i-th speaker, performs an adaptive operation in which the difference between the sound obtained by applying a frequency transfer function identical to the frequency transfer function from the i-th speaker to the i-th user to the sound output by the i-th sound source device and the output of a microphone placed at the i-th user's sound listening position, and the output of a microphone placed at the m-th user's sound listening position, is set as the frequency transfer characteristic of the i-th filter.

6. 2. The audio system of claim 1, An audio system characterized in that an adaptive filter, which receives as input the sound output by the i-th sound source device and whose output is the input to the i-th speaker, performs an adaptive operation in which the frequency transfer characteristic of the adaptive filter obtained as a result of weighting, with a predetermined weight, the difference between the sound obtained by applying the same frequency transfer function as the frequency transfer function from the i-th speaker to the i-th user to the sound output by the i-th sound source device and the output of a microphone placed at the sound listening position of the i-th user, and a value obtained by weighting, with a weight set for each microphone, the output of a microphone placed at the sound listening position of the m-th user, is set as the frequency transfer characteristic of the i-th filter.

7. 3. The audio system of claim 2, An audio system characterized in that an adaptive filter, which receives as input the sound output by the i-th sound source device and whose output is the input to the i-th speaker, performs an adaptive operation in which the difference between the sound obtained by applying a frequency transfer function identical to the frequency transfer function from the i-th speaker to the i-th user to the sound output by the i-th sound source device and the output of a microphone placed at the sound listening position of the i-th user, and the output of a microphone placed at the sound listening position of a target user, is set as the frequency transfer characteristic of the i-th filter.

8. 8. An audio system according to claim 1, 2, 3, 4, 5, 6 or 7, 11. An audio system according to claim 10, wherein each of said filters is a graphic equalizer.

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