JP4909058B2 - Noise reduction device - Google Patents

Description

  The present invention relates to a noise reduction device, and more particularly to an active control type noise reduction device that reduces noise by active control.

  Conventionally, environmental standards have been established for road traffic noise and railway noise, and road construction that does not meet the standards and operation of high-speed vehicles that do not meet the standards are not allowed.

  From such a background, sound barriers are actively developed, and active noise control (ANC) technology for reducing diffracted sound from the sound barriers by active control is being developed.

As ANC technology, a plurality of point sound sources are arranged in a straight line to form a finite-length control sound source, and a control sound is radiated from the control sound source in the front and diagonal directions, within the range of the width of the control sound source in the length direction. A noise reduction device for reducing noise is known (Patent Document 1).
JP 2006-138130 A

However, in the technique described in Patent Document 1 above, the range in which noise can be reduced is limited to the range of the width in the length direction of the control sound source, and thus noise that diffuses in a circular shape from the noise source is reduced over a wide range. There is a problem that you can not. In addition, there is a problem that it is impossible to cope with the movement of the position of the noise source.The present invention has been made to solve the above-described problems, and even if the position of the noise source moves. It is another object of the present invention to provide a noise reduction device that can reduce noise diffused from a noise source over a wide range even when there are a plurality of noise sources.

  In order to achieve the above object, the noise reduction device according to the first invention is arranged at intervals equal to or less than the length corresponding to 1/2 of the wavelength corresponding to the maximum frequency in the frequency band of the noise to be reduced. A speaker unit including a plurality of speakers, a microphone that collects noise from a noise source, and outputs an acoustic signal corresponding to the collected noise; and the noise source from the speaker unit based on the acoustic signal Generating means for generating a reduction signal for reducing noise on the opposite side, and the reduction signal, so that the envelope of the wave front of the control sound emitted from the speaker corresponds to the wave front of the noise Processing means for performing a process of delaying each time by a time corresponding to each of the distances to the plurality of speakers emitting the control sound based on the reduced signal delayed from the source; and processing by the processing means Input means for inputting the received signal to each of the plurality of speakers, position detection means for detecting the position of the noise source, and noise detected by the position detection means when the position of the noise source moves. Correction means for correcting the time delayed by the processing means so that the envelope of the wave front of the control sound emitted from the speaker corresponds to the wave front of the noise based on the position of the source Has been.

  According to the noise reduction device of the first invention, the microphone collects the noise from the noise source, outputs the acoustic signal corresponding to the collected noise, and the generating means generates the speaker based on the acoustic signal. A reduction signal is generated to reduce noise on the side opposite to the noise source from the unit.

  Then, the processing means emits the control signal based on the reduced signal delayed from the noise source so that the envelope of the wave front of the control sound emitted from the speaker corresponds to the wave front of the noise. A process of delaying by a time corresponding to each of the distances from the plurality of speakers is performed.

  Here, when the position of the noise source is moved, the position of the noise source is detected by the position detection means, and the sound is emitted from the speaker based on the position of the noise source detected by the position detection means by the correction means. The time delayed by the processing means is corrected so that the envelope surface of the control sound wavefront corresponds to the noise wavefront.

  Then, the signal processed by the processing means is input to each of the plurality of speakers by the input means, and the control sound is emitted by the plurality of speakers of the speaker unit. At this time, since the envelope of the wavefront of the sound wave obtained by synthesizing the emitted control sounds corresponds to the noise wavefront, the noise is reduced by the control sound.

  Thus, based on the position of the noise source, the delay time is corrected so that the envelope of the wave front of the control sound emitted from the plurality of speakers based on the reduction signal corresponds to the wave front of the noise, and each speaker By delaying the reduction signal input to the sound source and emitting the control sound from each speaker, the noise diffused from the noise source can be reduced over a wide range even if the position of the noise source moves.

  The noise reduction device according to the first aspect of the present invention collects noise from a noise source at a predetermined position with respect to each of the plurality of speakers, and is movable along the arrangement direction of the plurality of speakers. A second microphone that outputs an acoustic signal corresponding to the noise, and the position detecting means determines the position of the noise source based on the acoustic signal output by the microphone and the acoustic signal output by the second microphone. Can be detected. Thereby, the position of the noise source can be detected based on the acoustic signal corresponding to the noise from the noise source.

  The noise reduction device according to the first aspect of the present invention is installed at a predetermined position with respect to a corresponding speaker, collects noise from a noise source, and corresponds to the collected noise. The position detecting means further includes a plurality of second microphones for outputting an acoustic signal, and the position detecting means detects the position of the noise source based on the acoustic signals output by the microphone and the acoustic signals output by the plurality of second microphones. can do. Thereby, the position of the noise source can be detected based on the acoustic signal corresponding to the noise from the noise source.

  A noise reduction device according to a second invention is a speaker unit comprising a plurality of speakers arranged at intervals equal to or less than a length corresponding to 1/2 of the wavelength corresponding to the maximum frequency in the frequency band of noise to be reduced. Vibration detection means for detecting vibration of the noise source and outputting a vibration signal corresponding to the detected vibration, and for reducing noise on the side opposite to the noise source from the speaker unit based on the vibration signal Based on a reduction signal obtained by delaying the reduction signal with the noise source such that a generation means for generating a reduction signal and an envelope surface of the wave front of the control sound emitted from the speaker correspond to the wave front of the noise Processing means for performing a process of delaying each by a time corresponding to each of the distances from the plurality of speakers emitting the control sound, and signals processed by the processing means to the plurality of speakers An input means for inputting to each of them, a position detection means for detecting the position of the noise source, and the speaker based on the position of the noise source detected by the position detection means when the position of the noise source moves. And correction means for correcting the time delayed by the processing means so that the envelope of the wavefront of the control sound emitted from the sound corresponds to the wavefront of the noise.

  According to the noise reduction device of the second invention, the vibration detection unit detects the vibration of the noise source, outputs the vibration signal corresponding to the detected vibration, and the generation unit generates the speaker unit based on the vibration signal. A reduction signal for reducing noise on the side opposite to the noise source is generated.

  Then, the processing means emits the control signal based on the reduced signal delayed from the noise source so that the envelope of the wave front of the control sound emitted from the speaker corresponds to the wave front of the noise. A process of delaying by a time corresponding to each of the distances from the plurality of speakers is performed.

  Here, when the position of the noise source is moved, the position of the noise source is detected by the position detection means, and the sound is emitted from the speaker based on the position of the noise source detected by the position detection means by the correction means. The time delayed by the processing means is corrected so that the envelope surface of the control sound wavefront corresponds to the noise wavefront.

  Then, the signal processed by the processing means is input to each of the plurality of speakers by the input means, and the control sound is emitted by the plurality of speakers of the speaker unit. At this time, since the envelope of the wavefront of the sound wave obtained by synthesizing the emitted control sounds corresponds to the noise wavefront, the noise is reduced by the control sound.

  Thus, based on the position of the noise source, the delay time is corrected so that the envelope of the wave front of the control sound emitted from the plurality of speakers based on the reduction signal corresponds to the wave front of the noise, and each speaker By delaying the reduction signal input to the sound source and emitting the control sound from each speaker, the noise diffused from the noise source can be reduced over a wide range even if the position of the noise source moves.

  A noise reduction device according to a second invention is capable of moving along a direction in which a plurality of speakers are arranged and collecting noise from a noise source at a predetermined position with respect to each of the plurality of speakers. And a microphone for outputting an acoustic signal corresponding to the noise, and the position detecting means detects the position of the noise source based on the vibration signal output by the vibration detecting means and the acoustic signal output by the microphone. it can. Accordingly, the position of the noise source can be detected based on the vibration signal corresponding to the vibration of the noise source and the acoustic signal corresponding to the noise from the noise source.

  The noise reduction device according to the second invention is installed at a predetermined position with respect to each of the corresponding speakers, collects noise from a noise source, and corresponds to the collected noise. It further includes a plurality of microphones that output an acoustic signal, and the position detection means can detect the position of the noise source based on the vibration signals output by the vibration detection means and the acoustic signals output by the plurality of microphones. . Accordingly, the position of the noise source can be detected based on the vibration signal corresponding to the vibration of the noise source and the acoustic signal corresponding to the noise from the noise source.

  The position detection means according to the first and second inventions includes an imaging means for imaging a noise source, and can detect the position of the noise source based on an image captured by the imaging means.

  The position detection means according to the first and second inventions includes a GPS for positioning a predetermined position with respect to the noise source, and can detect the position of the noise source based on the predetermined position measured by the GPS.

  Further, in the noise reduction device according to the first and second inventions, when the frequency band of noise to be reduced is changed, the interval between the plurality of speakers is 1 of the wavelength corresponding to the maximum frequency in the frequency band. A moving means for moving the positions of the plurality of speakers so as to have an interval equal to or less than the length corresponding to / 2 can be further included. Thereby, even if the frequency band of noise changes, the noise diffused from the noise source can be reduced over a wide range.

  Further, a plurality of speakers of the above speaker unit can be provided on the wall.

  As described above, according to the noise reduction device of the present invention, based on the position of the noise source, the envelope surface of the wavefront of the control sound emitted from the plurality of speakers based on the reduction signal corresponds to the noise wavefront. The delay time is corrected so that the reduction signal input to each speaker is delayed, and the control sound is emitted from each speaker. Can be reduced over a wide range.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a case where the present invention is applied to a noise reduction system in a free sound field without a soundproof wall will be described.

  As shown in FIG. 1, the noise reduction system 10 according to the first embodiment controls a speaker unit 14 in which a plurality of speakers 12 are arranged in a row and a control sound emitted from the speakers 12. Control block 16, a plurality of power amplifiers 36 that amplify the signal output from the control block 16 and input to each speaker 12, and are installed near the noise source and collect noise from the noise source The sensor microphone 18 that outputs an acoustic signal corresponding to the collected noise, the microphone amplifier 20 that amplifies the acoustic signal, and the signal output from the microphone amplifier 20 are subjected to inverse filtering to generate a reduced signal. And an inverse filter DSP 22 serving as a generating means for outputting to the control block 16 and an error filter installed at the control point and fed back to the inverse filter DSP 22. And Maiku 24, a speaker near a microphone 38 provided close to the speaker 12, and a signal processing unit 40 as correction means for performing predetermined signal processing. As for the control point, since the sound wave from the noise source propagates in a spherical wave, it may be anywhere from the speaker unit 14 as long as it is opposite to the noise source. The power amplifier 36 corresponds to the input means of the present invention.

  In the speaker unit 14, a plurality of speakers 12 are arranged in a straight line, and the speaker 12 is controlled by the control block 16 so as to emit sound in a frequency band equal to or lower than the maximum frequency of the noise frequency band to be reduced. Is done.

Further, the plurality of speakers 12 are arranged at equal intervals, and the interval d is equal to the sound wavelength λ of the maximum center frequency Fmax of the frequency band to be reduced among the noise frequency bands, as shown by the following equation. 1/2 or less.
d ≦ λ / 2
For example, in the case of Fmax = 500 kHz, when the sound speed c is 340 m / s, the distance d is 0.34 m. The distance d between the speakers 12 may be equal to or less than λ / 2, and the maximum center frequency Fmax of the frequency band of noise to be reduced changes to a higher frequency Fmaxh, and the distance d is λmaxh / 2 (λmaxh). = C / Fmaxh), as shown in FIG. 2, a speaker moving means is provided by laying rails 13 along the arrangement position of the speakers 12 so that each of the speakers can be moved. If each speaker 12 is moved by a carriage 15 composed of a self-propelled wheel and an electric motor provided between the rail 13 and each speaker 12 so that the distance d to the frequency Fmaxh is λmaxh / 2 or less. Good. Note that the speaker 12 may be moved manually instead of a mechanical method such as an electric motor.

  The inverse filter DSP 22 includes an A / D converter 26 that converts an analog signal output from the microphone amplifier 20 into a digital signal, and an inverse filter 28 that does not change when a filter coefficient is set in advance. The filter coefficient of the inverse filter 28 is determined by either the explicit method or the LMS method, and outputs a signal having the same amplitude and opposite phase with respect to the signal output from the A / D converter 26.

  Further, the control block 16 includes a delay circuit 30 that delays signals according to the arrangement order of the speakers 12 and a D / A converter 34 that converts digital signals into analog signals for each of the n speakers 12. Are provided.

  The delay circuit 30 delays the signal input to the speaker 12 so that the virtual sound source of the speaker 12 is arranged in an arc shape centered on the noise source. The delay time of the signal input to each speaker 12 is determined by the signal processing unit 40 as follows.

  First, based on the sound wave information, the position of the noise source is obtained as follows. The cross spectrum Φxy (2) of the two sound waves x (t) and y (t) from the noise source incident on the sensor microphone 18 and the speaker proximity microphone 38 (Mi, i = 1, 2,..., 9 in this example). A cross-correlation function φxy (τ) that is an inverse Fourier transform of ω) is obtained.

  The cross-correlation function φxy (τ) is expressed as follows. The autocorrelation function for time functions x (t) and y (t) is

と表され、相互相関関数は

And the cross-correlation function is

と表される。ここで、φｘｘ（τ）、φｘｙ（τ）をフーリエ変換すると、パワースペクトルは、

It is expressed. Here, when φxx (τ) and φxy (τ) are Fourier transformed, the power spectrum is

と表され、クロススペクトルは、

And the cross spectrum is

と表される。また、系のインパルス応答をｈ（ｔ）とし、その伝達関数をＨ（ω）とすると、

It is expressed. If the impulse response of the system is h (t) and its transfer function is H (ω),

となる。また、周波数領域では以下のように表される。

It becomes. In the frequency domain, it is expressed as follows.

上記の相互相関関数φｘｙ（τ）は、センサーマイク１８を時間軸ゼロ（基点）として、騒音がセンサーマイク１８からスピーカ近接マイク３８（Ｍｉとする）に到達するまでに要する時間Ｔｉである。ここで、スピーカ近接マイク３８からセンサーマイク１８までの間の距離をｄｉとし、ｃを音速とすると、以下の式で表される。
Ｔｉ＝ｄｉ／ｃ
従って、センサーマイク１８からスピーカ近接マイク３８までの間の距離ｄｉは、ｄｉ＝Ｔｉ×ｃとなるため、スピーカ近接マイク３８の各々を円の中心として、半径ｄｉの円弧を描いて、円弧が交わる点を騒音源の位置として特定する。

The cross-correlation function φxy (τ) is the time Ti required for noise to reach the speaker proximity microphone 38 (Mi) from the sensor microphone 18 with the sensor microphone 18 as the time axis zero (base point). Here, when the distance from the speaker proximity microphone 38 to the sensor microphone 18 is di and c is the speed of sound, it is expressed by the following equation.
Ti = di / c
Accordingly, since the distance di from the sensor microphone 18 to the speaker proximity microphone 38 is di = Ti × c, each of the speaker proximity microphones 38 has an arc of radius di with each circle as the center, and the arcs intersect. The point is specified as the position of the noise source.

Note that the speaker proximity microphone 38 having the minimum time Tmin of Ti is the speaker proximity microphone 38 closest to the noise source, and when the distance from the sensor microphone 18 to the closest speaker proximity microphone 38 is R, the distance R is: It is expressed by the following formula.
R = Tmin · c
Then, as shown in FIG. 3, the speaker 12 closest to the sensor microphone 18 is set as the center speaker of the virtually arranged arcuate array speaker group, and as shown in FIG. 4, the delay time Δ when the center speaker is used as a reference. Is calculated by the following equation.
Δ = {(R ² + D _{± i} ² ) ^1/2 −R} / c (9)
When the position of the noise source moves, the delay time Δ is calculated for each speaker 12 based on the above formula, and the delay time Δ set in the delay circuit 30 corresponding to each speaker 12 is corrected. Thus, each of the delay circuits 30 delays the signal by the delay time Δ calculated according to the distance between the moved noise source and the speaker 12.

Further, the signal processing unit 40 calculates an amplitude correction K for correcting the amplitude of the control sound emitted from the speaker 12 and sets it in the delay circuit 30 as follows. When the speaker 12 is linearly arranged, the actual speaker 12 exists ahead by a distance corresponding to the delay time Δ with respect to the arc of the virtual arrangement, so that a louder sound than when the speaker 12 exists at the location of the virtual arrangement is generated. Release to control point. Therefore, a correction coefficient Ki for correcting the magnitude of the control sound to be small is calculated by the following equation.
Ki = Δi × c / R (I = 1, 2,...) (10)
In addition, the signal processing unit 40 determines the filter coefficient W (t) of the inverse filter 28 by, for example, an explicit method as follows.

  First, the cross-correlation function hs (t) between the noise x (t) from the noise source entering the sensor microphone 18 installed in the vicinity of the noise source and the noise ys (t) reaching the control point from the noise source is measured. , The cross-correlation function hc () between the noise x (t) from the noise source entering the sensor microphone 18 and the noise yc (t) emitted from the speaker 12 with the inverse filter set to W (t) = δ (t). t) is measured (measurement of impulse h (t) by cross-correlation method).

  Then, assuming that the transfer functions of hs (t) and hc (t) are Hs (ω) and Hc (ω), the inverse filter W (t) is determined by the following equation.

ここで、Ｆ^−１は逆フーリエ変換を示す。

Here, F ⁻¹ indicates an inverse Fourier transform.

  Next, the operation of the noise reduction system 10 according to the first embodiment will be described. First, the noise radiated from the noise source is collected by the sensor microphone 18, the acoustic signal is amplified by the microphone amplifier 20, and input to the inverse filter DSP 22. Then, the inverse filter 28 of the inverse filter DSP 22 performs digital filtering processing using the digital signal input from the A / D converter 26 and the set filter coefficient.

  At this time, by passing through the inverse filter 28, the waveform of the signal is shaped and time-shifted, and a reduced signal with the input signal in reverse phase is generated. Therefore, sound is emitted from the speaker 12 based on the reduced signal. A sound reduction effect can be obtained by the control sound.

  The reduced signal filtered by the inverse filter 28 is input to each delay circuit 30, and each delay circuit 30 delays the signal by a delay time set according to the arrangement order of the corresponding speakers 12. The delayed signal is input to the D / A converter 34, is D / A converted, and is output to the speaker unit 14 via the power amplifier 36. Then, a sound wave corresponding to the filtered signal, that is, a sound wave in the entire frequency band which is a reverse phase wave of noise is emitted from each speaker 12 of the speaker unit 14 toward the control point as a control sound.

  Further, when the noise source moves, the signal processing unit 40 identifies the position of the noise source based on the sound wave information of the sensor microphone 18 and the speaker proximity microphone 38, and the speaker 12 closest to the noise source position is selected. According to the distance from the speaker 12 to the noise source with the central speaker as a reference so that the control sound is emitted from the virtual sound source arranged on the arc centering on the position of the specified noise source as the central speaker. The delay time is calculated for each speaker 12, and the delay time set in each delay circuit 30 is corrected to the calculated correction time.

  Then, the reduced signal filtered by the inverse filter 28 is delayed by each delay circuit 30 by the corrected delay time. Based on the delayed signal, the noise from each speaker 12 of the speaker unit 14 is reduced. A sound wave in the entire frequency band, which is a reverse phase wave, is emitted as a control sound toward the control point.

  At this time, as shown in FIG. 5, since the control sound is emitted from the virtual sound source arranged on the arc centering on the destination noise source, it corresponds to the noise diffused in a circular shape from the noise source. The control sound is emitted in an arc shape, the control sound emitted from each speaker 12 is synthesized, and the synthesized sound wave becomes a spherical sound wave. The envelope of this wave front corresponds to the wave front of the noise from the noise source, and the control sound is in the opposite phase of the noise.

  Therefore, even if the position of the noise source moves, the noise from the noise source is canceled by the control sound from the speaker 12 over a wide range including the control point. FIG. 5 described above shows the movement of the noise source, but it is the same even when there are two sound sources, and shows that the speaker 12 works as two arcs. When there are two noise sources, as shown in FIG. 6, sensor microphones 18A and 18B, microphone amplifiers 20A and 20B, inverse filters DSPs 22A and 22B, and delay circuits 30A and 30B are provided for each noise source. Yes. Outputs from the delay circuits 30A and 30B for each of the plurality of noise sources are output to the D / A converters 34 having an addition function, and the speaker 12 of the speaker unit 14 is connected to each of the power amplifiers 36. A control sound is emitted.

  As described above, according to the noise reduction system according to the first embodiment, the envelope of the wave front of the control sound emitted from the plurality of speakers based on the reduced signal subjected to the inverse filtering process is the noise wave front. As described above, the noise diffused from the noise source can be reduced over a wide range by delaying the reduction signal input to each speaker and releasing the control sound from each speaker.

  Further, even when the noise source is moved and the position is changed, the position of the noise source is specified, and the sound emitted from the plurality of speakers based on the reduced signal is determined based on the specified position of the noise source. By correcting the delay time so that the envelope of the sound wavefront corresponds to the wavefront of the noise, delaying the reduction signal input to each speaker, and emitting the control sound from each speaker, the noise at the destination Noise spreading from the source can be reduced over a wide range.

  Further, active control can be performed even for a free sound field, that is, when there is no sound barrier, and noise can be reduced.

  In the above-described embodiment, the case where a plurality of speakers are arranged in a straight line has been described as an example. However, the present invention is not limited to this and may be arranged in an arc. Also in this case, for each speaker, the delay time is determined and set in the delay circuit based on the distance between the noise source and the speaker so that the virtual sound source of the speaker is arranged on the arc with respect to the noise source. do it.

  Next, a noise reduction system according to the second embodiment will be described. In addition, about the part which becomes the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The second embodiment is different from the first embodiment in that only one speaker proximity microphone is provided.

  As shown in FIG. 7, in the noise reduction system 210 according to the second embodiment, a wire 240 is provided along the arrangement direction of the plurality of speakers 12 of the speaker unit 14, and the speaker proximity microphone 238 is suspended from the wire. Thus, the speaker proximity microphone can be moved.

  When specifying the position of the noise source, the noise from the noise source is collected while moving the speaker proximity microphone 238 to a predetermined position close to each of the plurality of speakers 12, and the sound corresponding to the collected noise is collected. The signal is output to the signal processing unit 40.

  Thus, since only one speaker proximity microphone is required, a noise reduction system can be configured at low cost.

  Next, a noise reduction system according to the third embodiment will be described. In addition, about the part which becomes the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The third embodiment is different from the first embodiment in that the position of the noise source is specified based on the image information from the surveillance camera.

  As shown in FIG. 8, the noise reduction system 310 according to the third embodiment includes a monitoring camera 312 for imaging a noise source, and a signal processing unit 340 based on image information from the monitoring camera 312. The position of the noise source is specified, the center speaker is determined based on the position of the noise source, the delay time Δ is calculated for each speaker 12 according to the distance from the noise source with reference to the center speaker, The delay time Δ is set in the delay circuit 30 corresponding to 12.

  In the noise reduction system 310 according to the third embodiment, when the noise source moves, the noise source is imaged by the monitoring camera 312, and based on the image information of the monitoring camera 312 by the signal processing unit 340. Identify the location of the noise source. Further, the signal processing unit 340 calculates a delay time for each speaker 12 so as to emit a control sound from a virtual sound source arranged on an arc centered on the position of the identified noise source, and each delay time is calculated. The delay time set in the circuit 30 is corrected to the calculated correction time.

  Then, the reduced signal filtered by the inverse filter 28 is delayed by each delay circuit 30 by the corrected delay time. Based on the delayed signal, the noise from each speaker 12 of the speaker unit 14 is reduced. A sound wave in the entire frequency band, which is a reverse phase wave, is emitted as a control sound toward the control point.

  In the above embodiment, the case where the position of the noise source is specified by the image information of the monitoring camera is described as an example. However, an infrared sensor is provided, and the position of the noise source is specified by detecting the position using infrared rays. May be.

  Next, a noise reduction system according to the fourth embodiment will be described. In addition, about the part which becomes the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The fourth embodiment is different from the first embodiment in that the position of the noise source is specified based on the positioning information by GPS.

  As shown in FIG. 9, the noise reduction system 410 according to the fourth embodiment includes a GPS 412 for positioning the noise source position, and the GPS 412 is provided at substantially the same position as the noise source. The signal processing unit 440 specifies the position of the noise source based on the positioning information by the GPS 412, determines the center speaker based on the position of the noise source, and uses the center speaker as a reference according to the distance from the noise source. Then, the delay time Δ is calculated for each speaker 12, and the delay time Δ is set in the delay circuit 30 corresponding to each speaker 12.

  In the noise reduction system 410 according to the fourth embodiment, when the noise source moves, the GPS 412 determines the installation position of the GPS 412, and the signal processing unit 440 determines the noise source based on the positioning information of the GPS 412. Specify the position of. Further, the signal processing unit 440 calculates a delay time for each speaker 12 so as to emit a control sound from a virtual sound source arranged on an arc centered on the position of the specified noise source, and each delay time is calculated. The delay time set in the circuit 30 is corrected to the calculated correction time.

  Then, the reduced signal filtered by the inverse filter 28 is delayed by each delay circuit 30 by the corrected delay time. Based on the delayed signal, the noise from each speaker 12 of the speaker unit 14 is reduced. A sound wave in the entire frequency band, which is a reverse phase wave, is emitted as a control sound toward the control point.

  Next, a noise reduction system according to a fifth embodiment will be described. In addition, about the part which becomes the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 10, the noise reduction system according to the fifth embodiment is provided with a soundproof wall 550, and a plurality of speakers 12 of the speaker unit 14 are installed on the soundproof wall 550.

  As described above, even when the soundproof wall is provided, the noise diffused from the noise source can be reduced over a wide range. Even if the position of the noise source moves, the noise spread from the noise source is reduced over a wide range by correcting the delay time set in each delay circuit without moving the speaker on the sound barrier. be able to.

  In the first to fifth embodiments described above, a sensor microphone is used to collect noise from a noise source, and an acoustic signal corresponding to the collected noise is transmitted via a microphone amplifier. However, a vibration detector that detects the vibration of the noise source may be used. In this case, the vibration detector is used to detect the vibration of the noise source, and a vibration signal corresponding to the detected vibration is output to the inverse filter DSP via the microphone amplifier. A reduced signal may be generated by applying inverse filtering.

  Next, a noise reduction system according to the sixth embodiment will be described. In addition, about the part which becomes the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 11, the noise reduction system according to the sixth embodiment is provided with a soundproof wall 650 that is bent at an angle θ, and the plurality of speakers 12 of the speaker unit 14 are placed on the soundproof wall 650. Is installed.

  Thus, even when the soundproof wall is bent, the noise diffused from the noise source can be reduced over a wide range. Even if the position of the noise source moves, the noise spread from the noise source is reduced over a wide range by correcting the delay time set in each delay circuit without moving the speaker on the sound barrier. be able to.

  Next, a noise reduction system according to a seventh embodiment will be described. In addition, about the part which becomes the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 12, the noise reduction system according to the seventh embodiment is provided with a soundproof wall 750 extending in two straight lines, and the plurality of speakers 12 of the speaker unit 14 are It is installed on the soundproof wall 750.

  As described above, even when the soundproof wall is a two-step straight line, the noise diffused from the noise source can be reduced over a wide range. Even if the position of the noise source moves, the noise spread from the noise source is reduced over a wide range by correcting the delay time set in each delay circuit without moving the speaker on the sound barrier. be able to.

  The soundproof wall in which the speaker is arranged on the wall may have a curved shape centering on the side opposite to the noise source. Also in this case, the noise diffused from the noise source can be reduced over a wide range by delaying the reduction signal.

  Moreover, although the case where a soundproof wall is provided has been described as an example, even in a free sound field having no soundproof wall, as described above, without moving a plurality of speakers that are not arranged linearly, By correcting the delay time set in the delay circuit, the noise diffused from the noise source can be reduced over a wide range even if the noise source moves. For example, when the site boundary is not linear, the noise diffused from the noise source can be reduced over a wide range even when speakers are arranged along the site boundary.

It is the schematic which shows the structure of the noise reduction system which concerns on the 1st Embodiment of this invention. It is the schematic which shows the structure for the rail for moving a speaker, and a trolley | bogie. It is an image figure which shows the case where a center speaker is determined. It is an image figure which shows the case where a delay time is determined. It is an image figure which shows a mode that the position of a virtual sound source was changed by correct | amending the delay time of the delay circuit corresponding to a speaker, when the position of a noise source moved. It is the schematic which shows the structure of a noise reduction system in case there are two noise sources. It is the schematic which shows the structure of the noise reduction system which concerns on the 2nd Embodiment of this invention. It is the schematic which shows the structure of the noise reduction system which concerns on the 3rd Embodiment of this invention. It is the schematic which shows the structure of the noise reduction system which concerns on the 4th Embodiment of this invention. It is the schematic which shows the sound-proof wall and speaker of the noise reduction system which concern on the 5th Embodiment of this invention. It is the schematic which shows the sound-proof wall and speaker of the noise reduction system which concern on the 6th Embodiment of this invention. It is the schematic which shows the sound barrier and speaker of the noise reduction system which concerns on the 7th Embodiment of this invention.

Explanation of symbols

10, 210, 310, 410 Noise reduction system 12 Speaker 13 Rail 14 Speaker unit 15 Car 16 Control block 18 Sensor microphone 20 Microphone amplifier 22 Inverse filter DSP
26 A / D converter 28 Inverse filter 30 Delay circuit 34 D / A converter 36 Power amplifier 38, 238 Speaker proximity microphone 40, 340, 440 Signal processor 240 Wire 312 Monitoring camera 412 GPS
550, 650, 750 Sound barrier

Claims (10)

A speaker unit comprising a plurality of speakers arranged at intervals equal to or less than a length corresponding to ½ of the wavelength corresponding to the maximum frequency in the frequency band of noise to be reduced;
A microphone that collects noise from a noise source and outputs an acoustic signal corresponding to the collected noise;
Generating means for generating a reduction signal for reducing noise on the opposite side of the noise source from the speaker unit based on the acoustic signal;
The plurality of sound emitting control sounds based on the reduced signal obtained by delaying the reduced signal and the noise source so that an envelope surface of the wave surface of the controlled sound emitted from the speaker corresponds to the wave front of the noise. Processing means for performing a process of delaying each by a time corresponding to each of the distances to the speakers of
Input means for inputting the signal processed by the processing means to each of the plurality of speakers;
Position detecting means for detecting the position of the noise source;
Based on the position of the noise source detected by the position detection means when the position of the noise source moves, the envelope of the wave front of the control sound emitted from the speaker corresponds to the wave front of the noise. Correction means for correcting the time delayed by the processing means;
Noise reduction device including It is movable along the arrangement direction of the plurality of speakers, and collects noise from the noise source at a predetermined position with respect to each of the plurality of speakers, and an acoustic signal corresponding to the collected noise is obtained. A second microphone for outputting;
The noise reduction device according to claim 1, wherein the position detection unit detects the position of the noise source based on an acoustic signal output from the microphone and an acoustic signal output from the second microphone. Corresponding to each of the plurality of speakers, a plurality of second speakers are installed at predetermined positions with respect to the corresponding speakers, collect noise from the noise source, and output acoustic signals corresponding to the collected noise. Further including a microphone,
The noise reduction device according to claim 1, wherein the position detection unit detects a position of the noise source based on an acoustic signal output from the microphone and an acoustic signal output from the plurality of second microphones. A speaker unit comprising a plurality of speakers arranged at intervals equal to or less than a length corresponding to ½ of the wavelength corresponding to the maximum frequency in the frequency band of noise to be reduced;
Vibration detecting means for detecting vibration of a noise source and outputting a vibration signal corresponding to the detected vibration;
Generating means for generating a reduction signal for reducing noise on the side opposite to the noise source from the speaker unit based on the vibration signal;
The plurality of sound emitting control sounds based on the reduced signal obtained by delaying the reduced signal and the noise source so that an envelope surface of the wave surface of the controlled sound emitted from the speaker corresponds to the wave front of the noise. Processing means for performing a process of delaying each by a time corresponding to each of the distances to the speakers of
Input means for inputting the signal processed by the processing means to each of the plurality of speakers;
Position detecting means for detecting the position of the noise source;
Based on the position of the noise source detected by the position detection means when the position of the noise source moves, the envelope of the wave front of the control sound emitted from the speaker corresponds to the wave front of the noise. Correction means for correcting the time delayed by the processing means;
Noise reduction device including It is movable along the arrangement direction of the plurality of speakers, and collects noise from the noise source at a predetermined position with respect to each of the plurality of speakers, and an acoustic signal corresponding to the collected noise is obtained. A microphone for outputting;
The noise reduction device according to claim 4, wherein the position detection unit detects the position of the noise source based on a vibration signal output by the vibration detection unit and an acoustic signal output by the microphone. Corresponding to each of the plurality of speakers, a plurality of microphones installed at predetermined positions with respect to the corresponding speakers, collecting noise from the noise source, and outputting an acoustic signal corresponding to the collected noise In addition,
The noise reduction device according to claim 4, wherein the position detection unit detects a position of the noise source based on a vibration signal output by the vibration detection unit and an acoustic signal output by the plurality of microphones.   The noise reduction device according to claim 1, wherein the position detection unit includes an imaging unit that images the noise source, and detects the position of the noise source based on an image captured by the imaging unit.   The noise reduction device according to claim 1, wherein the position detection unit includes a GPS that measures a predetermined position with respect to the noise source, and detects the position of the noise source based on the predetermined position measured by the GPS. .   When the frequency band of the noise to be reduced changes, the interval between the plurality of speakers is equal to or less than the length corresponding to 1/2 of the wavelength corresponding to the maximum frequency in the frequency band. The noise reduction device according to claim 1, further comprising moving means for moving the positions of the plurality of speakers.   The noise reduction device according to claim 1, wherein a plurality of speakers of the speaker unit are provided on a wall.

Images