JP4428257B2 - Adaptive sound field support device - Google Patents

Description

  The present invention relates to a sound field support apparatus that enhances the sound effect based on existing room acoustic conditions, and more particularly, to a sound field support apparatus that can enhance the sound effect by suppressing the occurrence of howling even when installation conditions and sound field conditions are poor.

  In acoustic facilities such as concert halls and multipurpose halls, various music such as rock, pop and classical music is played. Such an acoustic facility is designed so that acoustic effects such as a feeling of reverberation, a feeling of volume, and a feeling of spreading are good. However, the acoustic effect differs depending on the size and structure of the acoustic facility and the type of music to be played. Therefore, it has been difficult to adjust the acoustic conditions of the acoustic facility so that all music can be played under optimal acoustic conditions.

Therefore, conventionally, a sound field control device has been disclosed that can naturally change the main acoustic effects related to architectural acoustics with the aid of electroacoustics (see, for example, Patent Documents 1 and 2).
Japanese Patent No. 2737595 Japanese Patent No. 2956642

  The sound field control devices disclosed in Patent Documents 1 and 2 are time-varying functions such as changing a combination of a microphone and a speaker in time or changing a filter in time (FM modulation) in order to suppress howling. Is introduced into the acoustic feedback system. However, in the sound field control devices disclosed in Patent Documents 1 and 2, specific conditions for howling are determined after construction. Therefore, it is indispensable to make adjustments to prevent howling after construction of the sound field control device, and it is necessary to adjust and equalize the loop gain while actually measuring the sound emitted from the device. There was a problem that it took time and effort.

  In addition, the sound field control devices disclosed in Patent Documents 1 and 2 amplify the reverberation component by collecting the reverberant sound emitted from the speaker with a microphone and looping the reverberant sound, feeling of volume, and spreading. Increase sound effects such as feeling. Therefore, in the above sound field control device, if the sound field conditions cannot secure a distance between the microphone and the speaker more than a predetermined distance as in a small space, the howling is controlled even if the sound field control function is provided as described above. It becomes difficult to do. Moreover, in order to suppress howling in the small space as described above, it is necessary to reduce the loop gain of the sound field control device. However, when the loop gain of the sound field control device is lowered, there is a problem that a sufficient acoustic effect cannot be obtained.

  Furthermore, the sound field control devices disclosed in Patent Documents 1 and 2 have a problem that the sound field conditions differ between adjustment and actual use of the hall. For example, the adjustment is performed with nothing on the stage. However, at the time of the opera performance, it will be in the state which installed the big tool on the stage. In addition, a plurality of performers are seated on the stage at the performance of the orchestra. Thus, if the state on the stage is different, the acoustic conditions of the hole change. Furthermore, even if the temperature and humidity in the hall change, the acoustic conditions of the hall change. Therefore, it is necessary to take a considerable margin when adjusting the sound field control device. However, there is a problem that the effect of the system is lowered as a result.

  Therefore, the present invention solves each of the above problems and can suppress the occurrence of howling even in a small space or an indoor space where the acoustic conditions change, and the acoustic effect by the initial reflected sound and the rear reverberant sound is good. An object of the present invention is to provide a sound field support device that can be used.

(1) a microphone that is installed in a room and collects sound emitted from a sound source and sound propagated from the surroundings;
A speaker that emits sound that supports the acoustics of the room;
A howling canceling means having an adaptive filter that estimates a transfer function of an acoustic feedback path from the speaker to the microphone and removes the feedback sound signal from the speaker from the collected sound signal of the microphone;
An initial reflected sound support signal generating means for convolving the collected sound signal from which the feedback sound signal has been removed and generating an initial reflected sound support signal that imitates an initial reflected sound generated in the room according to the sound emitted by the sound source; ,
A sound collecting signal from which the feedback sound signal has been removed is convoluted with a coefficient based on a transfer function estimated by the adaptive filter, and a sound emitted from the sound source is virtually connected to the room. Rear reverberation sound support signal generating means for generating a rear reverberation sound support signal simulating a rear reverberation sound generated by reverberating with the room;
An amplifier for outputting to the speaker before Symbol initial reflected sound assistance signal and amplifies the later reverberation assistance signal,
It is provided with.

  In this configuration, the adaptive sound field support apparatus estimates the transfer function of the acoustic feedback path from the speaker to the microphone using the adaptive filter, and removes the feedback sound signal from the speaker to the microphone from the collected sound signal of the microphone. Further, when the acoustic condition of the room changes, the adaptive filter updates the transfer function of the acoustic feedback path so as to attenuate the feedback sound according to the change. Furthermore, the adaptive sound field support device generates a simulated signal of the initial reflected sound emitted from the sound source in the indoor space by convolving the collected sound signal of the microphone from which the feedback sound signal has been removed based on the acoustic conditions in the indoor space. To do. In addition, in the adaptive sound field support apparatus, the coefficient of the rear reverberation sound generating means is set based on the transfer function of the acoustic feedback path estimated by the adaptive filter. Therefore, while canceling the feedback sound signal by the howling cancellation means to prevent / suppress the occurrence of howling, the acoustic effect of the early reflection sound and the rear reverberation sound, i.e., the reverberation feeling, volume feeling, and spreading feeling, can be adjusted to the acoustic conditions of the indoor space. Can be augmented (supported) based on Further, even if howling occurs, it is possible to quickly attenuate howling. Furthermore, the occurrence of howling can be suppressed even in a narrow indoor space where the distance between the microphone and the speaker is equal to or less than a predetermined distance and the conventional device is a condition for generating howling. Furthermore, even if the condition of the sound field in the indoor space changes, the feedback sound signal from the speaker to the microphone can be reliably removed from the collected sound signal of the microphone, and howling can be suppressed. In addition, by setting the coefficient based on the transfer function estimated by the adaptive filter, the rear reverberation sound generating means can be adjusted according to the state of the sound field in the room in which the adaptive sound field support apparatus is installed. Therefore, natural reverberation can be extended according to the state of the sound field in the room and its change.

(2) The rear reverberant sound support signal generating means sets a first FIR filter in which a filter coefficient based on an acoustic condition of the second room is set, and a filter coefficient based on a transfer function estimated by the adaptive filter A second FIR filter to be connected in a loop,
The collected sound signal from which the feedback sound signal has been removed is input to the input terminal of the first FIR filter, and a rear reverberant sound support signal is extracted from the output terminal of the first FIR filter.

  In this configuration, an acoustic loop is artificially created by connecting the first FIR filter and the second FIR filter in a loop shape. The second FIR filter is set with a filter coefficient based on the transfer function estimated by the adaptive filter, and the adaptive filter estimates the transfer function based on the state of the sound field in the room. Therefore, the filter coefficient of the second FIR filter can be changed according to the acoustic condition of the room and the change thereof. Therefore, the acoustic loop composed of the first FIR filter and the second FIR filter is used between the room in which the adaptive sound field support device is installed and the second room virtually connected to the room. A rear reverberation sound support signal simulating a rear reverberation sound generated by the sound emitted from the sound source being reflected can be generated. In addition, since the filter coefficients of the first FIR filter and the second FIR filter can be set to arbitrary values, the reverberation time of the rear reverberation sound can be extended and the level can be increased, and the acoustic effect of the indoor space can be increased. Can be strengthened.

  (3) Reverberation that determines an acoustic condition of the second chamber based on a transfer function estimated by the adaptive filter and sets a filter coefficient for the first FIR filter based on the determined acoustic condition. An adjustment means is provided.

  In the adaptive sound field support device, the first FIR filter and the second FIR filter are connected in a loop shape to create an acoustic loop artificially, and a room in which the adaptive sound field support device is installed; A rear reverberation sound support signal imitating a rear reverberation sound generated by reverberation of a sound emitted from a sound source is generated between the second room virtually connected to this room. In order to properly extend the reverberation time and increase the level of the rear reverberant sound, it is necessary to change the acoustic condition of the second chamber as the acoustic condition of the room changes. In this configuration, since the first filter coefficient can be set by the reverberation adjusting means, the acoustic condition of the second chamber can be easily changed according to the change of the acoustic condition of the room. Therefore, it is possible to appropriately extend the reverberation time and the level of the rear reverberant sound.

  (4) The reverberation adjusting means determines one or both of a sound absorption coefficient and a volume of the second chamber based on a transfer function estimated by the adaptive filter.

  In this configuration, the reverberation adjusting means determines the sound absorption coefficient and volume of the second chamber according to the acoustic conditions of the chamber. Therefore, the acoustic condition of the second chamber can be set to a desired value.

  (5) It is characterized by comprising loop gain adjusting means for measuring the loop gain of the first FIR filter and the second FIR filter connected in a loop and adjusting the loop gain to a preset value. To do.

  In this configuration, the loop gain of the rear reverberation generating means is adjusted to a preset value by the loop gain adjusting means. Therefore, on-site adjustment operations such as loop gain measurement and equalization, which are necessary when installing the conventional apparatus, can be greatly reduced.

  According to the present invention, since the transfer function that estimates the state and change of the sound field in order to remove the feedback sound that returns from the speaker to the microphone is used for adjusting the impulse response of the rear reverberant sound generation unit, the state of the sound field In addition, natural reverberation can be extended in response to changes, and the sound of indoor spaces can be supported in a stable state.

  Further, since it is possible to create a state in which the second room is virtually provided in the room in which the adaptive sound field support apparatus is installed, for example, the second room is similar to the room in which the adaptive sound field support apparatus is installed. The desired reverberation can be generated by setting a desired sound field.

  Furthermore, by removing the feedback sound signal that returns from the speaker to the microphone, even if the installation conditions of the microphone and speaker are limited, such as in a small space, the sound effect is enhanced based on the existing room acoustic conditions. Can help.

  In addition, the adaptive filter updates the transfer function of the acoustic feedback path to attenuate the feedback sound when the feedback sound from the speaker to the microphone changes. Even when the stage conditions change, such as in an opera performance, howling noise can be suppressed in accordance with the change.

  In addition, by removing the strong initial reflected sound that causes the howling, the loop gain of the acoustic feedback path can be minimized, and a sufficient control range can be secured.

  Furthermore, it is possible to estimate the loop gain in advance by artificially creating an acoustic loop with the FIR filter. In addition, since the loop gain of the acoustic loop is measured and adjusted to a preset value, the on-site adjustment work such as loop gain measurement and equalization required when installing a conventional sound field support device is performed. It can be greatly reduced.

  In the following description, the case where the adaptive sound field support apparatus of the present invention is provided in a small hall will be described as an example.

  FIG. 1 is a schematic layout diagram of an adaptive sound field support apparatus. A small hall 61, which is an example of an acoustic facility (room), includes a stage 65 and a guest seat 66. A musical instrument and its player (hereinafter referred to as a sound source 67) are located at the center of the stage 65, and a listener 68 is seated at the center of the audience seat 66. In the figure, the sound source 67 is displayed in a circle.

  FIG. 1 shows a case where eight sets of adaptive sound field support apparatuses are installed in the small hall 61. That is, the microphones 11-1 to 11-8 are arranged at a predetermined interval on the ceiling surface 62 of the small hole 61 so that sound propagating through the small hole 61 can be collected. Further, in order to support the sound of the small hall 61, that is, in order to emit the early reflection sound and the rear reverberation sound with extended reverberation time and level enhancement to the passenger seat 66, Speakers 53-1 to 53-4 are arranged on the wall surface 63, and a plurality of speakers 53-5 to 53-8 are arranged on the side wall surface 64 at predetermined intervals. The main body of the adaptive sound field support device is installed behind the scenes and in the adjustment room. Note that the arrangement of microphones and speakers and the number of adaptive sound field support devices to be used vary depending on the scale and shape of the acoustic facility. For example, the speaker may be arranged not only on the side wall surface but also on the ceiling surface, or may be arranged so as to emit a sound that supports the initial reflected sound or the rear reverberation sound from a speaker in which the sound emitting surface of the speaker faces the ceiling.

  FIG. 2 is a schematic block diagram of the adaptive sound field support apparatus. FIG. 3 is a diagram illustrating a state of the initial reflected sound and the rear reverberant sound generated by the adaptive sound field support apparatus.

  The adaptive sound field support apparatus 1 includes a sound collection unit 2, a howling cancellation unit 3, an initial reflected sound generation unit 4, a rear reverberation sound generation unit 5, an adder 6, and a sound emission unit 7.

  The sound collection unit 2 includes a microphone 11, a head amplifier 12, and an A / D converter 13. The howling cancellation unit 3 includes a delay circuit 21, an adaptive filter 22 including a filter unit 23 and a transmission system estimation unit 24, and an adder 25. The initial reflected sound generation unit 4 includes an FIR filter 31 and an equalizer 32. The rear reverberation sound generation unit 5 includes a reverberation sound generation filter 41, an adder 42, an FIR filter 43, an equalizer 44, an FIR filter 45, an equalizer 46, a reverberation sound reproduction filter 47, a loop gain measurement unit 48, and a reverberation adjustment unit 49. I have. The sound emitting unit 7 includes a D / A converter 51, a power amplifier 52, and a speaker 53.

  The sound collection unit 2 collects sound propagating in an indoor space such as the small hall 61, converts it into a digital signal, and outputs it. The microphone 11 is a sound that propagates from the surroundings, that is, a sound emitted directly from the sound source 67 (direct sound), or an early reflection sound that is generated when this sound is reflected by the wall of the small hall 61 or a tool on the stage 65. In addition, sound that propagates from the surroundings, such as the reverberant sound of the rear and the sound emitted from the speaker 53, is collected. The collected sound signal output from the microphone 11 is amplified by the head amplifier 12, digitized by the A / D converter 13, and output to the adder 25 of the howling cancellation unit 3.

  The howling cancellation unit 3 estimates the transfer function of the acoustic feedback path from the speaker 53 to the microphone 11 and removes the feedback sound signal from the speaker 53 collected by the microphone 11 from the collected sound signal of the microphone. Here, in the case where the howling cancellation unit 3 is not provided in the adaptive sound field support device 1, if the distance between the microphone 11 and the speaker 53 is equal to or less than a predetermined distance, the microphone 11 outputs the sound emitted from the speaker 53. Since the operation of collecting and amplifying with a gain of 1 or more is repeated, howling occurs. However, in the adaptive sound field support device 1, the feedback canceling signal from the speaker 53 picked up by the microphone 11 is removed from the picked-up signal of the microphone 11 by the howling canceling unit 3, thereby suppressing howling. be able to.

  The delay circuit 21 estimates the time delay of the feedback sound that is fed back from the speaker 53 to the microphone 11 and gives the time delay to the output signal of the adder 6. Then, the delay circuit 21 outputs a signal to the filter unit 23 and the transmission system estimation unit 24 of the adaptive filter 22.

  The adaptive filter 22 is a filter that simulates a sound transfer function in an acoustic feedback path that returns from the speaker 53 to the microphone 11, and filters the signal delayed by the delay circuit 21. Then, the adaptive filter 22 outputs the filtered signal to the adder 25 as a simulation signal.

  The filter unit 23 filters the signal output from the delay circuit 21 based on the transfer function of the acoustic feedback path estimated by the transfer system estimation unit 24 and outputs the filtered signal to the adder 25 as a simulated signal.

  The transmission system estimation unit 24 detects an erasure error of the feedback sound signal based on the past sound signal delayed by the delay circuit 21 and the current sound signal output from the adder 25. Then, the transfer system estimation unit 24 estimates and automatically updates the transfer function of the filter unit 23 so that the simulation signal matches or approximates the feedback sound signal. The transfer system estimation unit 24 updates the transfer function using an adaptive algorithm such as an LMS (Least Mean Square) algorithm. Further, the transfer system estimation unit 24 outputs the estimated transfer function to the FIR filter 45 and the reverberation adjustment unit 49.

  The adder 25 subtracts the output signal of the adaptive filter 22 from the sound collection signal output by the sound collection unit 2 and outputs the result. That is, the adder 25 subtracts the feedback sound signal fed back from the speaker 53 to the microphone 11 from the collected sound signal of the microphone 11 and outputs the result. The adder 25 outputs signals to the transmission system estimation unit 24, the FIR filter 31 of the initial reflected sound generation unit 4, and the reverberation sound generation filter 41 of the rear reverberation sound generation unit 5.

  The initial reflected sound generation unit 4 generates an initial reflected sound support signal that imitates the initial reflected sound that is generated when the sound emitted from the sound source 67 is reflected by the wall surface of the small hole 61 or the like. Further, the initial reflected sound generation unit 4 enhances (improves) the acoustic effect by extending the reverberation time or enhancing the level based on the existing room acoustic conditions.

  The FIR filter 31 is set with a filter coefficient based on the acoustic conditions of the small hole 61. The FIR filter 31 convolves the collected sound signal of the microphone 11 from which the feedback sound signal returning from the speaker 53 to the microphone 11 is removed, and generates a signal imitating the initial reflected sound generated in the small hall 61. Further, the FIR filter 31 enhances the level of the initial reflected sound and extends the reverberation time based on the existing room acoustic conditions, that is, the acoustic conditions of the small hall 61. Therefore, as shown in FIG. 3B, the initial reflected sound that sounds as if the space in the small hall 61 is expanded is emitted from the speaker 53 (not shown in FIG. 3B).

  The equalizer 32 is for adjusting the frequency characteristics and gain of the initial reflected sound, the time interval of each tap, and the like when the adaptive sound field support apparatus 1 is installed.

  The rear reverberation sound generation unit 5 generates a rear reverberation sound support signal that imitates the rear reverberation sound emitted from the sound source 67. Further, the rear reverberation sound generation unit 5 enhances (improves) the acoustic effect by extending the reverberation time or enhancing the level based on the existing room acoustic conditions.

  Here, the critical distance in the following description is a distance at which the energy balance between the direct sound emitted from the sound source 67 and the rear reverberation sound becomes equal. If the distance between the stage 65 and the microphone 11 is equal to or less than the critical distance, the direct sound emitted from the sound source 67 has larger energy than the rear reverberation sound. At this time, the microphone 11 cannot sufficiently collect the rear reverberation sound of the sound source 67. If the distance between the speaker 53 and the passenger seat 66 is less than or equal to the critical distance, the direct sound emitted from the speaker 53 has a larger energy than the rear reverberation sound. At this time, the reverberant sound cannot be sufficiently emitted from the speaker 53 to the space where the passenger seat 66 is installed.

  Here, an acoustic loop including the FIR filter 43, the equalizer 44, the FIR filter 45, the equalizer 46, and the adder 42 is referred to as a reverberation sound generation loop 50.

  The reverberation sound generation filter 41 is set with a filter coefficient based on the acoustic conditions of the small hall 61. That is, an impulse response that simulates the sound field of the small hall 61 where the adaptive sound field support apparatus 1 is installed or an impulse response that is actually measured in the small hall 61 is used.

  The reverberation sound generation filter 41 is set with a filter coefficient based on the acoustic conditions of the small hall 61. The reverberation sound generation filter 41 convolves the collected sound signal of the microphone 11 from which the feedback sound signal returning from the speaker 53 to the microphone 11 is removed, and generates a pseudo signal imitating the rear reverberation sound generated in the small hall 61. To do. For example, the reverberation sound generation filter 41 has a rear reverberation when the distance between the microphone 11 and the sound source 67 on the stage 65 is less than or equal to the critical distance, and the collected sound signal collected by the microphone 11 contains almost no reverberation sound. Generate and add sound pseudo signals. On the other hand, when the distance between the microphone 11 and the stage 65 exceeds the critical distance, the energy of the rear reverberant sound emitted from the sound source 67 is larger than that of the direct sound. In this case, since the microphone 11 can collect the rear reverberation sound emitted from the sound source 67, the function of the reverberation sound generation filter 41 is turned off, and the signal output from the adder 25 is the reverberation sound. It is set so as to pass through the generation filter 41.

  The adder 42 adds the signal output from the reverberation sound generation filter 41 and the signal output from the FIR filter 45 via the equalizer 46 and outputs a signal to the FIR filter 43.

  The FIR filter 43 is set with a filter coefficient based on the acoustic conditions of a coupled room 71 of a predetermined size virtually provided in the small hall 61. Further, the filter coefficient of the FIR filter 43 is set / changed by the reverberation adjusting unit 49. The FIR filter 43 outputs a signal to the FIR filter 45 and the reverberation sound reproduction filter 47 via the equalizer 44.

  The equalizer 44 is for adjusting the frequency characteristics and gain of the rear reverberant sound, the time interval of each tap, and the like when the adaptive sound field support apparatus 1 is installed.

  In the FIR filter 45, filter coefficients are set based on the transfer function estimated by the transfer system estimation unit 24. The transfer system estimation unit 24 estimates the transfer function of the acoustic feedback path from the speaker 53 to the microphone 11, and changes the transfer function accordingly when the sound field (acoustic condition) of the small hall 61 changes. Therefore, in the FIR filter 45, a filter coefficient based on the acoustic condition of the small hole 61 is set, and when the acoustic condition of the small hole 61 changes, the filter coefficient is updated. The FIR filter 45 outputs a signal to the adder 42 via the equalizer 46.

  Note that a filter coefficient can be set for the FIR filter 45 based on an impulse response actually measured in the small hall 61, and the filter coefficient can be changed based on the transfer function estimated by the transfer system estimation unit 24.

  The equalizer 46 is for adjusting the frequency characteristics and gain of the rear reverberant sound, the time interval of each tap, and the like when the adaptive sound field support apparatus 1 is installed.

  Here, in the present invention, the FIR filter 43 and the FIR filter 45 are connected in parallel in a loop shape, the signal output from the adder 25 is input from the input side of the FIR filter 43, and the signal is output from the output side of the FIR filter 43. By extracting the signal from the FIR filter 43 and the FIR filter 45, a signal simulating the rear reverberation sound can be circulated and output. Thereby, as shown in FIG. 3 (A), the state where the rear reverberant sound is reverberating between the small hall 61 as the original space and the coupled room 71 and the rear reverberant sound reaches the listener in the audience seat. Is simulated. Therefore, the sound generated by the sound source 67 is emitted from the speaker 53 as a reverberant sound generated by reverberation between the coupled room 71 connected to the small hall 61 and the small hall 61. Can do. Further, in the FIR filter 45, by setting the filter coefficient so as to increase the level of the reverberation sound and extend the reverberation time, the rear reverberation sound that sounds as if the space in the small hall 61 is expanded from the speaker 53. Sound can be emitted. In addition, since an arbitrary filter coefficient can be set in the FIR filter 43, the sound field of the coupled room 71 can be freely set according to the filter coefficient, and an arbitrary sound field can be used as the coupled room of the small hall 61. Can be set.

  The reverberation sound reproduction filter 47 is set with a filter coefficient based on the acoustic conditions of the small hall 61. That is, an impulse response that simulates the sound field of the small hall 61 where the adaptive sound field support apparatus 1 is installed or an impulse response that is actually measured in the small hall 61 is used. The reverberation sound reproduction filter 47 outputs the signal output from the FIR filter 43 when the distance between the speaker 53 and the passenger seat 66 is less than the critical distance and the reverberation sound cannot be emitted sufficiently to the passenger seat 66. A signal that imitates the rear reverberation generated in the small hall 61 is generated and output. On the other hand, when the distance between the speaker 53 and the passenger seat 66 exceeds the critical distance, the energy of the rear reverberant sound emitted from the sound source 67 is larger than that of the direct sound. In this case, since the sound simulating the rear reverberation sound emitted from the sound source 67 can be emitted from the speaker 53, the function of the reverberation sound reproduction filter 47 is turned off, and the signal simulating the rear reverberation sound. Is set to pass through the reverberation sound reproduction filter 47.

  The loop gain measurement unit 48 measures the loop gain of the reverberation sound generation loop 50 based on the input signal level and output signal level of the reverberation sound generation loop 50. Then, the loop gain measurement unit 48 adjusts the set value by outputting a signal to the equalizer 44 and the equalizer 46 so that the loop gain of the rear reverberation sound generation unit 5 becomes a preset value. Further, the loop gain measuring unit 48 adjusts the equalizer 44 and the equalizer 46 so that the level of the simulated signal of the rear reverberant sound and the level of the simulated signal of the initial reflected sound become a predetermined ratio. The equalizer 32 of the generation unit 4 is adjusted.

  The reverberation adjustment unit 49 determines the acoustic condition of the coupled room 71 based on the transfer function estimated by the transmission system estimation unit 24, and sets / changes the filter coefficient of the FIR filter 43 based on the acoustic condition. For example, the acoustic conditions of the small hall 61 (sound field) are different between the case where an instrument is installed on the stage 65 in an opera performance and the case where only the performer is on the stage 65 in an orchestra performance. ), It is necessary to change the acoustic conditions of the coupled room 71 as well. In such a case, in the present invention, the filter coefficient of the FIR filter 43 is changed by the reverberation adjusting unit 49, and the acoustic effect of the support signal of the rear reverberant sound is adjusted according to the change in the sound field.

  FIG. 4 is a graph showing a state of improvement of the acoustic effect by the FIR filter. As shown in FIG. 4A, the reverberation adjusting unit 49 applies an exponential function factor on the time axis to the transfer function estimated by the transfer system estimating unit 24. Thereby, in the impulse response characteristic of the FIR filter 43, the inclination of the reverberation attenuation curve changes, so that the acoustic effect of the rear reverberant sound can be changed as if the average sound absorption coefficient of the coupled room 71 is changed. Further, the reverberation adjusting unit 49 changes the sampling period with respect to the transfer function estimated by the transfer system estimating unit 24, as shown in FIG. Thereby, since the impulse response characteristic of the FIR filter 43 expands and contracts on the time axis, the acoustic effect of the rear reverberant sound can be changed as if the room size (volume of the room) of the coupled room 71 is changed. Thus, the acoustic condition of the coupled room 71 can be set to a desired value.

  The adder 6 adds the initial reflected sound support signal that is an output signal of the initial reflected sound generation unit 4 and the rear reverberation sound support signal that is an output signal of the rear reverberation sound generation unit 5. The adder 6 outputs both signals to the sound emission unit 7 and the howling cancellation unit 3.

  The digital signal output from the adder 6 to the sound emission unit 7 is converted into an analog signal by the D / A converter 51. The power amplifier 52 amplifies the initial reflected sound support signal simulating the initial reflected sound and the rear reverberant sound support signal simulating the rear reverberant sound, and outputs both signals to the speaker 53. The speaker 53 emits a sound simulating the initial reflection sound and the rear reverberation sound of the sound emitted from the sound source 67.

  Next, the adjustment operation at the time of installing the adaptive sound field support apparatus 1 of the present invention will be described. When the adaptive sound field support apparatus 1 is installed in the small hall 61, if the distance between the microphone 11 and the stage 65 is less than the critical distance, the rear reverberation sound of the sound source 67 is output by the microphone 11 as described above. Can't pick up enough sound. In this case, the function of the reverberation sound generation filter 41 is turned on, and a simulation signal of the rear reverberation sound of the sound emitted from the sound source 67 is generated from the sound collection signal of the microphone 11. Thereby, the reverberation time is extended between the small hall 61 and the coupled room 71 and the reverberation time is extended, and the rear reverberation sound having an enhanced level can be generated.

  On the other hand, when the distance between the microphone 11 and the stage 65 exceeds the critical distance, the energy of the rear reverberant sound emitted from the sound source 67 is larger than that of the direct sound. In this case, since the rear reverberation sound emitted from the sound source 67 can be collected by the microphone 11, the reverberation sound generation filter 41 is turned off and the signal is set to pass through the reverberation sound generation filter 41. To do. As a result, the rear reverberant sound picked up by the microphone 11 is further reflected from the speaker 53 simulating a state in which the rear reverberant sound is reflected in the coupled room 71 and a state in which it is reflected between the coupled room 71 and the small hall 61. Sound can be emitted.

  Further, when the adaptive sound field support apparatus 1 is installed in the small hall 61, if the distance between the speaker 53 and the listener 68 of the passenger seat 66 is less than the critical distance, as described above, The reverberant sound cannot be emitted sufficiently. In this case, the function of the reverberation sound reproduction filter 47 is turned on, and a simulation signal of the rear reverberation sound emitted from the sound source 67 on the stage 65 is generated and output. As a result, it is possible to generate a rear reverberant sound that reverberates in the small hall 61 and the coupled room 71 and finally propagates in the small hall 61 and propagates to the passenger seat 66 and emits the sound from the speaker 53.

  On the other hand, when the distance between the speaker 53 and the listener 68 in the passenger seat 66 exceeds the critical distance, the energy of the reverberant sound emitted from the sound source 67 is greater than that of the direct sound. In this case, since the rear reverberation sound emitted from the sound source 67 can be emitted from the speaker 53, the reverberation sound reproduction filter 47 is turned off, and the rear reverberation sound support signal passes through the reverberation sound reproduction filter 47. Set to Thereby, the rear reverberation sound that reverberated in the small hall 61 and the coupled room 71 can be emitted from the speaker 53, and this sound can finally be reverberated in the small hall 61 and propagated to the passenger seat 66.

  Next, the frequency characteristics and the like of the FIR filter 31, the FIR filter 43, and the FIR filter 45 are adjusted by equalizing the equalizer 32, the equalizer 44, and the equalizer 46. At this time, the sound emitted from the sound source 67 and the reverberation sound propagated from the surroundings are picked up by the microphone 11, and the desired reflected sound is confirmed while confirming the initial reflection sound and the rear reverberation sound emitted from the speaker 53. Make adjustments to achieve the effect.

  In the adaptive sound field support device 1, the impulse response characteristics set in the FIR filter 31, the FIR filter 43, and the FIR filter 45 are changed and adjusted, and the reverberation at each tap of the impulse response as shown in FIG. By changing the slope of the attenuation curve, an acoustic effect can be obtained as if the average sound absorption rate in the indoor space is changed. In addition, as shown in FIG. 4B, by changing the interval between the taps of the impulse response, the acoustic effect as if the room size was changed can be obtained.

  For example, since the impulse response corresponding to the coupled room 71 is set in the FIR filter 43, the sound field can be changed by changing the impulse response characteristic set in the FIR filter 43, and the sound of the rear reverberation sound can be changed. Characteristics can be changed. Moreover, a more natural sound can be created by using the impulse response actually measured for the FIR filter. Furthermore, since the acoustic loop is artificially created by the FIR filter 43 and the FIR filter 45, the loop gain can be estimated in advance. Therefore, on-site adjustment operations such as loop gain measurement and equalizing, which require time for adjustment in the conventional sound field support apparatus, can be greatly reduced.

  Next, the operation of the adaptive sound field support apparatus 1 will be described. The adaptive sound field support device 1 is configured to output a sound emitted from the sound source 67 on the stage 65, a sound propagated from the surroundings, and a sound emitted from the speaker 53 (the initial reflection sound of the sound emitted from the sound source 67). And a sound simulating a rear reverberation sound) are collected by the microphone 11. The howling cancel unit 3 estimates a transfer function of an acoustic feedback path from the speaker 53 to the microphone 11, and generates a simulation signal that simulates the feedback sound signal from the speaker 53 collected by the microphone 11. The adder 25 removes the feedback signal collected by the microphone 11 from the collected signal of the microphone 11 and outputs a signal to the initial reflected sound generation unit 4 and the rear reverberation sound generation unit 5.

  The initial reflected sound generation unit 4 generates an initial reflected sound support signal of the sound source 67 and outputs it to the adder 6. Further, the rear reverberation sound generation unit 5 generates and adds a simulation signal of the rear reverberation sound of the sound source 67 according to the change in the sound field of the small hall 61 based on the transfer function output from the transmission system estimation unit 24. To the device 6. The adder 6 outputs to the speaker 53 a rear reverberation support signal that simulates the initial reflection sound and the rear reverberation sound of the sound source 67. From the speaker 53, a sound imitating the initial reflection sound and the rear reverberation sound of the sound source 67 is output.

  As described above, the adaptive sound field support apparatus 1 according to the present invention generates a sound simulating a rear reverberation sound based on the transfer function estimated by the transfer system estimation unit 24, so that the sound field in the indoor space can be changed. Accordingly, the sound imitating the rear reverberation can be changed. Therefore, the adjustment work performed when installing the adaptive sound field support apparatus can be greatly reduced. Even if the acoustic conditions of the small hall 61 change, the acoustic effect of the rear reverberation sound and the early reflection sound can be automatically changed, so there is no need to take a margin when adjusting the device, and the effect of the system can be improved. Can be improved.

  Further, the adaptive sound field support apparatus 1 of the present invention includes the howling cancellation unit 3 using the adaptive filter 22, so that a change in temperature or a change in the sound field occurs, or a large amount installed on the stage 65. Howling can be prevented even if conditions such as tools change. Further, in the adaptive sound field support apparatus 1 of the present invention, the feedback signal from the speaker 53 to the microphone 11 can be removed by the howling cancel unit 3, so that a small space in which the distance between the microphone and the speaker is equal to or less than the critical distance. Even so, it is possible to enrich the reverberant sound based on the existing room acoustic conditions without generating howling.

  The acoustic conditions of the room will be determined immediately before the performance starts and at the start of the performance. Therefore, the adjustment of the FIR filter 45 based on the transfer function estimated by the transfer system estimation unit 24 and the adjustment of the FIR filter 43 by the reverberation adjustment unit 49 are performed only once before the performance starts or when the curtain opens. It is good to configure.

  In the above description, the adaptive sound field support device according to the present invention is described as an example provided in a small hall. However, the present invention is not limited to this, and sounds such as sound facilities and listening rooms can be heard. Any room can be applied as long as the room reflects and generates an early reflection sound and a rear reverberation sound. For example, even when the adaptive sound field support apparatus according to the present invention is provided in a large hall or a middle hall, the reverberation of the initial reflected sound and the rear reverberation sound can be enriched with a slight adjustment.

  In the above description, the case where the FIR filter is used for the initial reflected sound generation unit 4 and the rear reverberation sound generation unit 5 has been described as an example. However, the present invention is not limited to this and other filters are used. May be. For example, an IIR filter or the like can be used.

It is a schematic layout of an adaptive sound field support device. It is a block diagram which shows schematic structure of an adaptive sound field assistance apparatus. It is a figure which shows the state of the early reflection sound and rear reverberation sound which an adaptive type sound field assistance apparatus produces | generates. It is a graph which shows the state of the improvement of the acoustic effect by a FIR filter.

Explanation of symbols

1-adaptive sound field support device 2-sound pickup unit 3-howling cancellation unit 4-early reflected sound generation unit 5-rear reverberation sound generation unit 6-adder 7-sound emission unit 11-microphone 12-head amplifier 13- A / D converter 21-delay circuit 22-adaptive filter 23-filter unit 24-transmission system estimation unit 25-adder 31, 43, 45-FIR filter 32, 44, 46-equalizer 41-reverberation sound generation filter 42-addition Device 47-reverberation sound reproduction filter 48-loop gain measurement unit 49-reverberation adjustment unit 50-reverberation sound generation loop 51-D / A converter 52-power amplifier 53-speaker 61-small hall 65-stage 66-passenger seat 67-sound source 68-listener 71-coupled room

Claims (5)

A microphone that is installed in the room and picks up the sound emitted by the sound source and the sound propagated from the surroundings;
A speaker that emits sound that supports the acoustics of the room;
A howling canceling means having an adaptive filter that estimates a transfer function of an acoustic feedback path from the speaker to the microphone and removes the feedback sound signal from the speaker from the collected sound signal of the microphone;
An initial reflected sound support signal generating means for convolving the collected sound signal from which the feedback sound signal has been removed and generating an initial reflected sound support signal that imitates an initial reflected sound generated in the room according to the sound emitted by the sound source; ,
A sound collecting signal from which the feedback sound signal has been removed is convoluted with a coefficient based on a transfer function estimated by the adaptive filter, and a sound emitted from the sound source is virtually connected to the room. Rear reverberation sound support signal generating means for generating a rear reverberation sound support signal simulating a rear reverberation sound generated by reverberating with the room;
An amplifier for outputting to the speaker before Symbol initial reflected sound assistance signal and amplifies the later reverberation assistance signal,
An adaptive sound field support device characterized by comprising: The rear reverberant sound support signal generating means includes a first FIR filter in which a filter coefficient based on an acoustic condition of the second room is set, and a filter coefficient based on a transfer function estimated by the adaptive filter. 2 FIR filters are connected in a loop,
2. The adaptation according to claim 1, wherein a collected sound signal from which the feedback sound signal is removed is input to an input terminal of the first FIR filter, and a rear reverberant sound support signal is extracted from an output terminal of the first FIR filter. Type sound field support device.   Reverberation adjusting means for determining an acoustic condition of the second chamber based on a transfer function estimated by the adaptive filter and setting a filter coefficient for the first FIR filter based on the determined acoustic condition. The adaptive sound field support apparatus according to claim 2 provided.   4. The adaptive sound field support apparatus according to claim 3, wherein the reverberation adjusting unit determines one or both of a sound absorption coefficient and a volume of the second chamber based on a transfer function estimated by the adaptive filter.   The loop gain adjustment means for measuring the loop gain of the first FIR filter and the second FIR filter connected in a loop and adjusting the loop gain to a preset value. The adaptive sound field support apparatus according to claim 1.

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