Audio systems and in-car systems

Abstract

To provide an "audio system and on-vehicle system" capable of effectively suppressing a sound leakage to an outside of a vehicle by a comparatively simple configuration.SOLUTION: A sound X1(f) output by an i-th audio source apparatus ASi is adjusted by a frequency transmission function Wii(f) which is set in a sound leakage reduction filter Wi by an i-th sound leakage reduction filter Wi, so as to be output from an i-th speaker SPKi to a user Pi. In the sound leakage reduction filter Wi, the frequency transmission function Wii(f) is set so as to allow a sound to be comparatively smaller in the case of a frequency where a gain from the SPKi to one or more predetermined sound leakage reference positions tends to be comparatively larger compared with the gain of the frequency transmission function from the SPKi to the user Pi, and to allow the sound to be comparatively louder in the case of a frequency where a gain tends to be comparatively smaller.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a technique for suppressing sound leakage of an audio system mounted on an automobile to the outside of the vehicle.

Background Art

[0002] As a technique for suppressing sound leakage of an audio system mounted on an automobile to the outside of the vehicle, there is known a technique of providing an external speaker that outputs sound toward the outside of the vehicle, and outputting, from the external speaker, sound having an inverted phase of the output sound of the audio system as a cancellation sound that cancels the output sound of the audio system outside the vehicle (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the technique of outputting a cancellation sound from the above-described external speaker, an external speaker is separately required in addition to the speakers of the audio system. Further, according to this technique, since the sound leakage of the output sound of the audio system can be suppressed only in the vicinity of the external speaker, when suppressing the sound leakage of the audio system to the outside of the vehicle in a wide direction range, a large number of external speakers are required. Therefore, when attempting to sufficiently suppress the sound leakage of the audio system to the outside of the vehicle by this technique, an increase in the scale and complexity of the configuration are inevitable. Therefore, an object of the present invention is to suppress sound leakage of an audio system mounted on an automobile to the outside of the vehicle with a relatively simple configuration.

Means for Solving the Problems

[0005] To achieve the above objectives, the present invention provides an audio system mounted in an automobile comprising a sound source device, a speaker, and a filter that transmits the sound output by the sound source device to the speaker with a set frequency transfer characteristic. However, the frequency transfer characteristic set in the filter is the gain of the frequency transfer function from the speaker to the listening position of the target user, who is seated in a predetermined seat in the automobile. do From the speaker, to the automobile I want to reduce sound leakage. The gain of the frequency transfer function to the reference position, which is a position near the car outside the car. direction but big In terms of frequency, sound is Make it smaller , with respect to the gain of the frequency transfer function from the speaker to the sound listening position of the target user do , the gain of the frequency transfer function up to the aforementioned reference position direction but small In terms of frequency, sound is Large Let this be the frequency transfer function.

[0006] In this audio system, the reference position may be a position near the speaker. Furthermore, in order to achieve the above objectives, the present invention provides an audio system mounted in an automobile that includes a sound source device, a speaker, and a filter that transmits the sound output by the sound source device to the speaker with a set frequency transfer characteristic. However, the frequency transfer characteristic set in the filter is the gain of the frequency transfer function from the speaker to the listening position of the target user, who is seated in a predetermined seat in the automobile. do From the speaker, to the automobile I want to reduce sound leakage. The gain of the frequency transfer function to multiple reference positions that are mutually distinct locations near the automobile outside the automobile. direction but big In terms of frequency, sound is Make it smaller , with respect to the gain of the frequency transfer function from the speaker to the sound listening position of the target user do , the gain of the frequency transfer function up to the plurality of reference positions direction but small For the frequency, the sound Large shall have the frequency transfer function.

[0007] Here, in this audio system, the number of the plurality of reference positions is L, and the frequency transfer function from the speaker to the listening position of the sound of the target user is C 11 (f), the complex conjugate of C 11 (f) is C * 11 (f), the frequency transfer function from the speaker to the z-th (where z is an integer from 1 to L) reference position is C iz (f), the complex conjugate of C iz (f) is C * iz (f), and the frequency transfer characteristic W 11 set for the i-th filter may be [[ID=二十四]]<00001

[0008]

Number

[0009] expressed as follows. <00 > Alternatively, in this audio system, the frequency transfer characteristic of the adaptive filter obtained as a result of causing an adaptive operation to be performed, where the error is the difference between the sound obtained by applying the same frequency transfer function as the frequency transfer function from the speaker to the listening position of the sound of the target user to the sound output from the sound source device in advance and the output of the microphone arranged at the listening position of the user's sound, and the output of the microphone arranged at each of the plurality of reference positions, may be the one set as the frequency transfer characteristic in the filter.

[0010] Alternatively, the audio system may be configured such that the frequency transfer characteristics of an adaptive filter, which takes the sound output from the sound source device as input and the output as input to the speaker, are set as the frequency transfer characteristics of the adaptive filter, which is configured to set as an error if the difference between the sound output from the sound source device and the output of a microphone placed at the user's listening position is weighted by a predetermined weight, and the output of a plurality of microphones placed at each of the plurality of reference positions is weighted by a weight set for each microphone.

[0011] Furthermore, in order to achieve the above objectives, the present invention provides an audio system mounted in an automobile that includes a sound source device, a plurality of speakers from the 1st to the nth (where n>2), and a plurality of filters from the 1st to the nth (where n>2). The i-th filter (where i is an integer from 1 to n) transmits the sound output by the sound source device to the i-th speaker with a set frequency transfer characteristic. The frequency transfer characteristic set for the i-th filter is the gain of the frequency transfer function from the speaker to the listening position of the target user, who is seated in a predetermined seat in the automobile. do From the i-th speaker, to the automobile I want to reduce sound leakage. The gain of the frequency transfer function to the i-th reference position, which is the position near the i-th speaker outside the automobile. direction but big In terms of frequency, sound is Make it smaller , with respect to the gain of the frequency transfer function from the i-th speaker to the sound listening position of the target user do The ratio of the gains of the frequency transfer function up to the i-th reference position is small In terms of frequency, sound is Large Let this be the frequency transfer function.

[0012] In the audio system described above, the filter may be a graphic equalizer. Furthermore, the system may be configured to include multiple such audio systems, with each audio system designating different seats among the multiple seats in the vehicle as the predetermined seats. With the audio system described above, it is possible to suppress speaker output sound leaking outside the vehicle with a relatively simple configuration that only requires a filter to adjust the output sound of the sound source device transmitted to the speaker according to the set frequency transmission characteristics, while minimizing the reduction in the volume and perceived sound quality of the speaker output sound that the user can hear. [Effects of the Invention]

[0013] As described above, according to the present invention, sound leakage from an audio system installed in an automobile to the outside of the vehicle can be suppressed with a relatively simple configuration. [Brief explanation of the drawing]

[0014] [Figure 1] This is a block diagram showing the configuration of an audio system according to the first embodiment of the present invention. [Figure 2] This figure shows an example of speaker arrangement in an audio system according to the first embodiment of the present invention. [Figure 3] This figure shows an example of microphone placement during the learning of the transfer function of the sound leakage reduction filter according to the first embodiment of the present invention. [Figure 4] This figure shows the configuration for learning the transfer function of a sound leakage reduction filter according to the first embodiment of the present invention. [Figure 5] This figure shows another example of learning the transfer function of the sound leakage reduction filter according to the first embodiment of the present invention. [Figure 6] This is a block diagram showing the configuration of an audio system according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described below. First, the first embodiment will be described. Figure 1 shows the configuration of the audio system according to this first embodiment. The audio system is a system installed in a car, and it has n subsystems SSi, where i is a number from 1 to n. The i-th subsystem SSi comprises the i-th audio source device ASi, the i-th sound leakage reduction filter Wi, and the i-th SPKi. The subsystem SSi is a system for the i-th seat of a car, and the audio source device ASi is a device that outputs sound to be heard by user Pi, who is seated in the i-th seat. In subsystem SSi, the sound Xi(f) output by the audio source device ASi is filtered by a sound leakage reduction filter Wi, and the frequency transfer function W set in the sound leakage reduction filter Wi is used. ii The output is adjusted by (f) and is output from speaker SPKi, which is located near the i-th seat and radiates sound towards the user Pi.

[0016] Hereinafter, we will explain using the example where n=4, i is a number from 1 to 4, the first seat of the car is the right front seat, the second seat is the left front seat, the third seat is the right rear seat, and the fourth seat is the left rear seat. In this case, as shown in Figure 2, for example, speaker SPK1 of subsystem SS1 is located in the right front door of the car, speaker SPK2 of subsystem SS2 is located in the left front door, speaker SPK3 of subsystem SS3 is located in the right rear door, and speaker SPK4 of subsystem SS4 is located in the left rear door.

[0017] Here, the frequency transfer function W of the sound leakage reduction filter Wi of the i-th subsystem SSi. ii (f) is calculated and set in advance as follows: Here, the frequency transfer function W ii The calculation of (f) uses Q microphones, from microphone MC1 to microphone MCQ (Q>2). In the following explanation, we will assume that Q=5 and use 5 microphones, from microphone MC1 to microphone MC5. Frequency transfer function W of sound leakage reduction filter W1 of subsystem SS1 11 When calculating (f), as shown in Figure 3a, microphone MC1 is placed at the listening position of the user seated in the first seat, the right front seat, and microphones MC2, MC3, MC4, and MC5 are placed at predetermined external sound leakage reference positions. Here, the sound leakage reference positions are four external positions near speakers SPK1, SPK2, SPK3, and SPK4.

[0018] Furthermore, the frequency transfer function W of the sound leakage reduction filter W2 of subsystem SS2 22 When calculating (f), the arrangement of microphones MC2, MC3, MC4, and MC5 is the same as in Figure 3a, as shown in Figure 3b, and microphone MC1 is placed at the listening position of the user seated in the second seat, the left front seat.

[0019] Furthermore, the frequency transfer function W of the sound leakage reduction filter W3 of subsystem SS3 33 When calculating (f), the arrangement of microphones MC2, MC3, MC4, and MC5 is the same as in Figure 3a, as shown in Figure 3c, and microphone MC1 is placed at the listening position of the user seated in the third seat, the right rear seat.

[0020] Furthermore, the frequency transfer function W of the sound leakage reduction filter W4 of subsystem SS4 44 When calculating (f), the arrangement of microphones MC2, MC3, MC4, and MC5 is the same as in Figure 3a, as shown in Figure 3d, and microphone MC1 is placed at the listening position of the user seated in the left rear seat, which is the fourth seat.

[0021] Then, the frequency transfer function W of the sound leakage reduction filter Wi of the i-th subsystem SSi. ii (f) is calculated using the configuration shown in Figure 4. As shown in the diagram, this configuration includes an audio source device ASi, a target setting unit 301, an adaptive filter 302, a speaker SPKi, five microphones MC1 to MC5 as described above, and five subtractors AD1 to AD5. The target setting unit 301 is equipped with five filters 3011 that take the output Xi(f) of the audio source device ASi as input. The i-th filter 3011 sets the target frequency transfer function H from speaker SPKi to the j-th microphone MCj (where j is a number from 1 to 5). ij (f) is set.

[0022] The adaptive filter 302 includes a variable filter 3021 that takes the output Xi(f) of the audio source device AS1 as input, and an adaptive algorithm execution unit 3022, with the output of the variable filter 3021 being output from the speaker SPKi. The j-th adder ADj has a frequency transfer function H ij (f) is the output T of the j-th filter 3011 that has been set. j (f) Output Y of the j-th microphone MCj j Subtract (f) and get the j-th error E j (f) is output to adaptive filter 302. The adaptive algorithm execution unit 3022 of the adaptive filter 302 executes a predetermined adaptive algorithm such as Multiple Error Filtered-X LMS (MENLSM) and adjusts the frequency transfer characteristic G of the variable filter 3021 so that the five errors E1(f) to E5(f) output from the five subtractors AD1-AD5 are minimized overall. ii Perform an adaptive action to update the system.

[0023] In this configuration, while the audio source device ASi outputs Xi(f), the adaptive algorithm execution unit 3022 performs adaptive operation, and the frequency transfer characteristic G of the variable filter 3021 is determined. ii If it converges, then the converged frequency transfer characteristic G ii The frequency transfer function W is set to the sound leakage reduction filter Wi of subsystem SSi. ii (f)

[0024] Here, the first filter 3011 of the target setting unit 301 sets the target frequency transfer function H from speaker SPKi to user Pi. i1 (f) is set as the frequency transfer function H of the second and subsequent filters 3011 of the target setting unit 301. i2 From H i5 Set it so that the gain is 0 for all frequencies.

[0025] In this case, the actual frequency transfer function from speaker SPKi to microphone MCj up to the jth position is C. ij The frequency transfer function W is calculated by expressing it as follows: ii (f) is A * The complex conjugate of A is given by equation 1.

[0026]

number

[0027] The frequency transfer function W of the sound leakage reduction filter Wi of subsystem SSi, calculated and set in this manner. ii (f) According to C i1 Compared to the gain from speaker SPKi to user Pi (microphone MC1) shown by (f), C is a number between 2 and 5, where m is a number between 2 and 5. im As shown in (f), at frequencies where the gain from speaker SPKi to the sound leakage reference position (microphone MC2-MC5) tends to be high, the sound is made relatively quieter, and compared to the gain from speaker SPKi to user Pi (microphone MC1), C im At frequencies where the gain from the speaker (SPKi) indicated by (f) to the sound leakage reference position (microphones MC2-MC5) tends to be low, the sound leakage reduction filter Wi adjusts the volume to be relatively louder.

[0028] As a result, sound leakage can be effectively suppressed in a way that minimizes the reduction in volume and perceived sound quality of the output sound from speaker SKIi that the i-th user Pi can hear. By the way, the frequency transfer function W of the sound leakage reduction filter Wi of the i-th subsystem SSi described above ii (f) is calculated by setting up multipliers MP1 to MP5 as shown in Figure 5, and multiplier MPj calculates the error E output by ADj. j Alternatively, (f) may be multiplied by the weight Kj and output to the adaptive filter 302.

[0029] Also, as mentioned above, if m is a number from 2 to 5, C im * (f) C im (f) / C i1 * (f) C i1 (f) Let d be the value of m that maximizes the error E d Error E other than (f) m (f) The weight Km is set to 0, and the error E d (f) and the weight Kd of error E1(f), K1 can be set to 1, in which case the frequency transfer function W set to the sound leakage reduction filter Wi ii (f) is given by equation 2.

[0030]

number

[0031] Note that in the case of the microphone MCj arrangement shown in Figure 3, C im * (f) C im (f) / C i1 * (f) C i1 (f) C is maximized im (f) is the frequency transfer function C from speaker SKI to the i+1th microphone MC(i+1) closest to it. i(i+1) Since this can be expected, we unconditionally set d=i+1, and error E dError E other than (f) m (f) The weight Km is set to 0, and the error E d The weights Kd and K1 of (f) and error E1(f) may be set to 1.

[0032] Alternatively, if the microphone placed at the sound leakage reference position where you want to suppress sound leakage the most is designated as the microphone MCR, and d=R, then error E d Error E other than (f) m (f) The weight Km is set to 0, and the error E d The weights Kd and K1 of (f) and error E1(f) may be set to 1.

[0033] By doing so, it is possible to most effectively reduce the output sound of the speaker SKI to the external sound leakage reference location where the sound leakage is most loudly audible, or to the sound leakage reference location where sound leakage should be most suppressed. Also, the frequency transfer function W ii The amount of processing required for the adaptive operation of the adaptive algorithm execution unit 3022, which is necessary for calculating (f), can also be reduced.

[0034] The first embodiment of the present invention has been described above. A second embodiment of the present invention will be described below. Figure 6 shows the configuration of the audio system. In the audio system according to this second embodiment, unlike the first embodiment, all SPKi are used for user P1 in the front left seat, which is the first seat. As shown in the diagram, this audio system comprises one audio source device AS1, four sound leakage reduction filters Wi, and four SPKi, where i is a number from 1 to 4. The sound Xi(f) for SPKi output by the audio source device ASi is filtered through the sound leakage reduction filter Wi, and the frequency transfer function W set in the sound leakage reduction filter Wi is used. ii (f) is adjusted and output from speaker SPKi. Frequency transfer function W of sound leakage reduction filter Wi ii (f) is calculated and set in advance. Frequency transfer function W of sound leakage reduction filter Wi ii The calculation of (f) is performed in the configuration shown in Figure 3a, with microphones MC1 and MC5 arranged, and then in Figure 4 or Figure 5, with audio source device ASi replaced by audio source device AS1.

[0035] Note that the frequency transfer function W of the i-th sound leakage reduction filter Wi ii When calculating (f), the output of all speakers except the i-th speaker SPKi is stopped. Furthermore, in Figure 5, the frequency transfer function W is shown in the configuration where audio source device ASi is replaced with audio source device AS1. ii When calculating (f), as mentioned above, we unconditionally set d=i+1, and error E d Error E other than (f) m (f) The weight Km is set to 0, and the error E d The weights Kd and K1 of (f) and error E1(f) may be set to 1.

[0036] Thus, the frequency transfer function W of the four sound leakage reduction filters Wi ii By performing the calculation of (f) independently, the four sound leakage reduction filters Wi will have different characteristics. Therefore, it is expected that the output sounds of the four speakers SKIi, each adjusted by the different characteristics of the four sound leakage reduction filters Wi, will complement each other, thereby suppressing the degradation of the sound quality of the output sound of the audio source device AS1 heard by the user P1.

[0037] Embodiments of the present invention have been described above. In each of the above embodiments, the function of the sound leakage reduction filter Wi is to adjust the gain of the output sound Xi(f) of the audio source device for each frequency. Therefore, as the sound leakage reduction filter Wi, a graphic equalizer that adjusts the gain for each frequency band, such as every 1 / 3 octave band, may be used. [Explanation of symbols]

[0038] AS...Audio source device, AD...Subtractor, MC...Microphone, MP...Multiplier, P...User, SPK...Speaker, W...Sound leakage reduction filter, 301...Target setting unit, 302...Adaptive filter, 3011...Filter, 3021...Variable filter, 3022...Adaptive algorithm execution unit.

Claims

1. An audio system installed in a car, Sound source device and Speakers and, The sound source device has a filter that transmits the sound output by the sound source device to the speaker with a set frequency transmission characteristic, The frequency transfer characteristics set in the filter are such that the sound is reduced at frequencies where the gain of the frequency transfer function from the speaker to a reference position, which is a position near the car outside the car where sound leakage should be suppressed, is greater than the gain of the frequency transfer function from the speaker to the listening position of the target user, which is a user seated in a predetermined seat in the car, and the sound is increased at frequencies where the gain of the frequency transfer function to the reference position is less than the gain of the frequency transfer function from the speaker to the listening position of the target user.

2. The audio system according to claim 1, The audio system is characterized in that the reference position is a position near the speaker.

3. An audio system installed in a car, Sound source device and Speakers and, The sound source device has a filter that transmits the sound output by the sound source device to the speaker with a set frequency transmission characteristic, The frequency transfer characteristics set in the filter are such that the sound is reduced at frequencies where the gain of the frequency transfer function from the speaker to a plurality of mutually different reference positions outside the car near the vehicle where sound leakage to the car should be suppressed is greater than the gain of the frequency transfer function from the speaker to the listening position of the target user seated in a predetermined seat in the car, and the sound is increased at frequencies where the gain of the frequency transfer function to the plurality of reference positions is less than the gain of the frequency transfer function from the speaker to the listening position of the target user.

4. The audio system according to claim 3, Let the number of the plurality of reference positions be L, and let the frequency transfer function from the speaker to the sound listening position of the target user be C 11 (f), C 11 The complex conjugate of (f) is C * 11 (f), and let the frequency transfer function from the speaker to the z-th (where z is an integer from 1 to L) reference position be C iz (f), C iz The complex conjugate of (f) is C * iz (f), and the frequency transfer characteristic W set for the i-th filter is 11 as follows [Math 1] An audio system characterized by being represented as such.

5. The audio system according to claim 3, An audio system characterized in that an adaptive filter, which takes the sound output from the sound source device as its input and the output as the input to the speaker, is pre-configured to perform an adaptive operation in which the difference between the sound output from the sound source device, obtained by applying the same frequency transfer function from the speaker to the listening position of the target user, and the output of a microphone placed at the user's listening position, and the output of microphones placed at each of the multiple reference positions, is set as the frequency transfer characteristic of the adaptive filter.

6. The audio system according to claim 3, An audio system characterized in that an adaptive filter, which takes the sound output from the sound source device as its input and the output as the input to the speaker, is set as the frequency transfer characteristic of the adaptive filter as an error when the difference between the sound output from the sound source device and the output of a microphone placed at the user's listening position is weighted by a predetermined weight, and the output of a plurality of microphones placed at each of the plurality of reference positions is weighted by a weight set for each microphone, is set as the frequency transfer characteristic of the adaptive filter.

7. An audio system installed in a car, Sound source device and Multiple speakers from the 1st to the nth (where n > 2), It has multiple filters from the 1st to the nth (where n > 2), The i-th filter (where i is an integer from 1 to n) filters the sound output by the sound source device. The signal is transmitted to the i-th speaker using the set frequency transfer characteristics. The audio system is characterized in that the frequency transfer characteristics set in the i-th filter are a frequency transfer function that reduces the sound at frequencies where the gain of the frequency transfer function from the i-th speaker to the i-th reference position, which is a position outside the car near the i-th speaker where sound leakage to the car is to be suppressed, is greater than the gain of the frequency transfer function from the speaker to the listening position of the target user, which is a user seated in a predetermined seat in the car, and increases the sound at frequencies where the gain of the frequency transfer function to the i-th reference position is less than the gain of the frequency transfer function from the i-th speaker to the listening position of the target user.

8. An audio system according to claim 1, 2, 3, 4, 5, 6, or 7, The aforementioned filter is a graphic equalizer, and is used in this audio system.

9. A plurality of audio systems according to claim 1, 2, 3, 4, 5, or 6 are provided. An in-vehicle system characterized in that each audio system is an audio system that designates different seats among the multiple seats of the vehicle as predetermined seats.

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