JP6298656B2 - Noise reduction device and noise reduction system - Google Patents

Description

  The present invention relates to a noise reduction device and a noise reduction system, and more particularly to an active control type noise reduction device and a noise reduction system for reducing 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.

  Further, as an ANC technique, a general control method of a feedback type active sound reduction system for reducing low frequency sound of an engine of a construction machine is known (for example, Patent Document 1). This control method is a method of installing a secondary sound source in the vicinity of the exhaust port having the largest noise value.

  In addition, a method is known in which a radiation source of a secondary sound source is installed in the vicinity of an exhaust port by attaching a flexible reducer to a speaker (for example, Patent Document 2).

JP 2010-24876 A JP 2011-241745 A

  However, with the technique described in Patent Document 1, the secondary sound source may not be installed in the immediate vicinity of the exhaust port depending on the shape of the construction machine. For example, when a speaker is installed using a stepladder, a sound source with a fixed position can be handled, but a moving sound source cannot be handled. Therefore, there is a problem that applicable models are limited.

  Further, the technique described in Patent Document 2 has a problem in that the radiation sound pressure is attenuated from the secondary sound source due to the change in the cross-sectional area of the sound wave propagation path by attaching the reducer. This is fatal to reduce noise with a high sound pressure level at low frequencies such as engine sound. For example, the sound pressure level near the exhaust port of a large generator may reach 95 dB or more in the low sound range, and a large-diameter unit and a large box are required as a secondary sound source. However, due to the decrease in the sound pressure level of the secondary sound source due to the reducer installation, a larger speaker system is required. It is not easy to make a secondary sound source that exceeds a sound pressure level of 95 dB in a low frequency band.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a noise reduction device and system capable of reducing low frequency noise regardless of the type and shape of the noise source. And

In order to achieve the above object, a noise reduction device according to the present invention emits a control sound on the side opposite to a noise source arranged in a casing having an exhaust port, and a plurality of noise reduction devices arranged adjacent to each other. A speaker unit including a speaker, and a duct portion having openings at both ends, wherein an opening on one end side is provided at an exhaust port of the housing , and noise from the noise source is transmitted to the plurality of the speaker units. A duct section that leads to the opening on the other end provided in the middle section between the speakers, and collects noise on the opposite side of the noise source from the speaker unit, and outputs an acoustic signal corresponding to the collected noise Based on the acoustic signal, generating means for generating a reduction signal for reducing noise on the side opposite to the noise source from the speaker unit, and a reduction signal generated by the generating means The is configured to include a input means for inputting to the plurality of loudspeakers.

  According to the noise reduction device of the present invention, the duct portion guides noise from the noise source to an intermediate portion between the plurality of speakers of the speaker unit. The microphone collects the noise on the side opposite to the noise source from the speaker unit, outputs an acoustic signal corresponding to the collected noise, and generates the sound from the speaker unit on the side opposite to the noise source based on the acoustic signal. A reduction signal for reducing noise is generated.

  Then, the reduction signal generated by the generation unit is input to each of the plurality of speakers by the input unit, and the control sound is emitted by the plurality of speakers of the speaker unit. At this time, noise is reduced by the control sound emitted from the plurality of speakers.

  In this way, the noise from the noise source is guided to the middle part between the plurality of speakers of the speaker unit by the duct portion, and the noise is reduced by the control sound emitted from the plurality of speakers. Regardless of the type and shape, low frequency noise can be reduced.

  The speaker unit according to the present invention can be arranged in an opening provided as an exhaust port of a soundproof sheet provided so as to cover the noise source. Thereby, low frequency noise can be effectively reduced by combination with the vowel sheet.

  The noise source according to the present invention may be a plurality of noise sources, and the duct portion may be a plurality of duct portions provided for the plurality of noise sources. As a result, low frequency noise can be effectively reduced with respect to a plurality of noise sources.

  The noise source according to the present invention is a plurality of noise sources having different noise frequencies, and the opening on the other end side of the plurality of duct portions is provided in the middle portion between the plurality of speakers. A noise source arranged so as to be arranged in a direction orthogonal to the arrangement direction of the speakers and having a higher noise frequency can be arranged at a position closer to a line connecting the centers of the plurality of speakers. Thereby, low frequency noise can be effectively reduced with respect to a plurality of noise sources having different noise frequencies.

  A silencer member can be provided inside the duct part. Thereby, high-frequency noise can also be reduced.

  Said duct part can be made into a bellows-like flexible duct. Thereby, high-frequency noise can also be reduced.

  The noise reduction system according to the present invention is a soundproof sheet provided so as to cover the noise reduction device and the noise source, wherein the speaker unit is disposed in an opening provided as an exhaust port. It is comprised including the sheet | seat.

  As described above, according to the noise reduction device and the noise reduction system of the present invention, the duct part guides the noise from the noise source to the middle part between the plurality of speakers of the speaker unit, and from the plurality of speakers. By reducing the noise by the emitted control sound, it is possible to reduce the noise of the low frequency sound regardless of the type and shape of the noise source.

It is the schematic which shows the structure of the noise reduction system which concerns on the 1st Embodiment of this invention. It is a top view which shows the structure of the noise reduction system which concerns on the 1st Embodiment of this invention. It is a front view which shows the structure of the noise reduction system which concerns on the 1st Embodiment of this invention. It is a graph which shows the relationship between the distance between a noise source and a secondary sound source, and the frequency reduced. It is a functional block diagram which shows the structure of the noise reduction apparatus which concerns on the 1st Embodiment of this invention. It is a graph which shows the measurement result of the sound pressure level of the engine exhaust port upper part of a noise source. It is a graph which shows the volume reduction of the noise of each frequency in each measurement location. It is a figure which shows embodiment which has arrange | positioned the speaker unit on the vehicle body of a heavy construction machine.

<First Embodiment>
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 that reduces noise radiated from an engine exhaust port of a construction machine will be described.

  As shown in FIG. 1, the noise reduction system 10 according to the first embodiment of the present invention includes a plurality of construction machines 12, a soundproof sheet 14 provided so as to cover the plurality of construction machines 12, and a soundproof sheet. Corresponding to the plurality of speakers 16 and the speaker unit 17 including a plurality of speakers 16 provided side by side in the vicinity of the exhaust outlet 14A of the fourteen and emitting sound toward the noise reduction area outside the soundproof sheet 14. A plurality of error microphones 18 provided for feedback, a noise reduction device 20 that emits sound from a plurality of speakers 16 to reduce noise based on inputs from the plurality of error microphones 18, and a plurality of An opening on one end side is provided near the engine exhaust port 12A of the construction machine 12 so as to correspond to the construction machine 12, and the engine exhaust port 12 of the construction machine 12 is provided. Noise from, a, a plurality of flexible duct 22 for guiding to the opening portion of the intermediate portion provided with the other end side (see FIG. 2) between the plurality of speakers 16.

  The plurality of construction machines 12 are, for example, a generator, a compressor, and a mobile crane, and each have an engine exhaust port.

  The plurality of speakers 16 of the speaker unit 17 are installed in the direction in which sound reduction is desired, that is, toward the outside of the soundproof sheet 14.

  The flexible duct 22 is a bellows-like duct and has flexibility. One end of the flexible duct 22 is opened near the engine exhaust port 12 </ b> A of the construction machine 12, and the other end is opened at an intermediate portion between the plurality of speakers 16.

  As shown in FIG. 3, the opening on the other end side of each of the plurality of flexible ducts 22 is arranged in an intermediate portion (see FIG. 2) between the plurality of speakers 16 so as to be arranged in the vertical direction. .

  Here, FIG. 4 shows the relationship between the distance between the noise source and the speaker and the frequency of the noise to be reduced by 5 dB to 20 dB. As can be seen from FIG. 4, the higher the noise between the noise source and the speaker, the lower the high frequency noise.

  Therefore, in the present embodiment, among the plurality of construction machines 12, the opening on the other end side of the flexible duct 22 in which an opening on one end side is set near the engine exhaust port 12A of the construction machine 12 having a high noise frequency. However, it is arranged at a position close to a line connecting the centers of the plurality of speakers 16. On the other hand, among the plurality of construction machines 12, the opening on the other end of the flexible duct 22 in which an opening on one end is set near the engine exhaust port 12A of the construction machine 12 having a low noise frequency is the other flexible. It arrange | positions in the position (for example, upper side) far from the line | wire which connected the center of the some speaker 16 from the opening part of the other end side of the duct 22. As shown in FIG.

  As shown in FIG. 5, the noise reduction apparatus 20 includes a D / A converter 62 that converts a digital signal into an analog signal, and a power that amplifies the signal output from the D / A converter 62 and inputs the amplified signal to the speaker 16. An amplifier 42, a microphone amplifier 48 that amplifies an acoustic signal from the error microphone 18, a subtractor 50 that takes a difference between a signal output from the microphone amplifier 48 and a signal output from the D / A converter 62, and subtraction On the basis of the acoustic signal from the inverse filter DSP 46 as a generation unit that generates a reduced signal by applying inverse filtering to the signal output from the converter 50 and outputs the reduced signal to the D / A converter 62, and the microphone amplifier 48. An inverse filter computing unit 54 that computes the inverse filter and sets the inverse filter in the inverse filter DSP 46. A combination of the D / A converter 62, the power amplifier 42, the microphone amplifier 48, the subtractor 50, the inverse filter DSP 46, and the inverse filter calculation unit 54 is provided for each pair of the speaker 16 and the error microphone 18. ing. The power amplifier 42 corresponds to input means of the present invention.

  The inverse filter DSP 46 includes an A / D converter 56 that converts the analog signal output from the subtractor 50 into a digital signal, an inverse filter 58 in which a filter coefficient is set, and a predetermined frequency band (for example, 100 Hz) to be reduced. And a band-pass filter 60 that performs filtering so as to pass the following signal. The filter coefficient of the inverse filter 58 is calculated by the inverse filter calculation unit 54 by, for example, the filtered-X LMS method. The inverse filter 58 performs a filtering process using an inverse filter on the signal output from the A / D converter 56, thereby outputting a signal having the same amplitude and opposite phase outside the speaker 16. Note that an anti-aliasing low-pass filter (not shown) is provided at the front stage of the A / D converter 56 and the rear stage of the D / A converter 62.

  The inverse filter calculation unit 54 inputs x (t) entering the error microphone 18 and the output ys (t) from the subtractor 50 to the LMS system, and performs filter coefficient by automatic identification by the operation of the filtered-X LMS method. W (t) is determined and stored in a memory (not shown) in the inverse filter 58.

  Next, the operation of the noise reduction system 10 according to the present embodiment will be described.

  First, noise radiated from the engine exhaust port of each construction machine 12 is guided to the middle part of the speaker 16 of the speaker unit 17 by each flexible duct 22 and collected by each error microphone 18 together with the control sound from the speaker 16. The acoustic signal is amplified by each microphone amplifier 48 and input to each inverse filter operation unit 54 and each inverse filter DSP 46 via the subtractor 50.

  Then, each inverse filter computing unit 54 computes the filter coefficient of the inverse filter based on the acoustic signal from the error microphone 18 and the output signal from the subtractor 50 according to the filtered-X LMS method. Store in memory.

  The inverse filter 58 of each inverse filter DSP 46 performs digital filtering processing using the digital signal input from the A / D converter 56 and the set filter coefficient.

  At this time, by passing through the inverse filter 58, 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 each speaker 16 based on the reduced signal. The sound reduction effect can be obtained by the control sound.

  The reduced signal filtered by each inverse filter 58 is input to each band pass filter 60, and only a signal in a predetermined frequency band passes, and the passed signal is input to each D / A converter 62. Then, each D / A converter 62 performs D / A conversion, and outputs to each speaker 16 via each power amplifier 42. Then, the sound wave corresponding to the filtered signal, that is, a noise anti-phase wave, and a sound wave in a predetermined frequency band are emitted from each speaker 16 toward the outside of the soundproof sheet 14 as a control sound. The Therefore, on the outside of the soundproof sheet 14, the noise from each construction machine 12 is canceled by the control sound from each speaker 16.

  Further, high-frequency noise of noise radiated from the engine exhaust port of each construction machine 12 is reduced in each flexible duct 22 when guided to the middle portion of the speaker 16 of the speaker unit 17 by each flexible duct 22. Is done.

  As described above, according to the noise reduction system according to the first embodiment, the flexible ducts guide the noise from the plurality of construction machines to the middle part between the plurality of speakers of the speaker unit, and The noise is reduced by the control sound emitted from the speaker. In this way, by installing a flexible duct at the engine exhaust port of the construction machine and extending it to the vicinity of the speaker of the noise feedback type ANC system, it is low regardless of the type and shape of the construction machine that is the noise source. Frequency noise can be effectively reduced.

  Also, since the inside of the flexible duct can be subjected to sound absorption processing, the sound pressure level radiated from the opening of the flexible duct can be lowered, and the sound pressure level radiated from the speaker unit can be reduced. It is also possible to reduce the size of the speaker.

  Further, when the entire construction machine is surrounded by a soundproof sheet for soundproofing, the noise reduction device according to the present embodiment is effective. In order to release the exhaust heat and exhaust from the engine exhaust port of construction machinery to the outside, the intake and exhaust port must be extended outside the enclosure with a duct or the like. Therefore, the noise from the exhaust port having the largest noise value cannot be reduced by the soundproof sheet. In the present embodiment, by setting the position of the opening of the duct in the vicinity of the speaker of the ANC system, the noise from the exhaust port can be reduced, and the entire noise source can be reduced.

  In addition, by reducing low-frequency noise emitted from engine exhaust ports of construction machinery, current construction noise can be reduced to a lower level than before, contributing to the conservation of the surrounding noise environment. it can. Although the restriction or shortening of the operation / operation time of a construction machine is greatly related to the progress of the construction, the adoption of the noise reduction system according to the present embodiment makes it possible to largely avoid this problem. This can contribute to reducing the influence of noise on the work schedule.

<Second Embodiment>
Next, a noise reduction system according to the second embodiment will be described. In addition, since the noise reduction system which concerns on 2nd Embodiment is the structure similar to 1st Embodiment, it attaches | subjects the same code | symbol and abbreviate | omits description.

  The second embodiment is different from the first embodiment in that a silencing member (silence chamber) is provided in each flexible duct.

  In the noise reduction system 10 according to the second exemplary embodiment, a noise reduction member (for example, a noise reduction chamber) is provided in each flexible duct 22. As a result, high-frequency noise of noise radiated from the engine exhaust port of each construction machine 12 is guided to the middle portion of the speaker 16 of the speaker unit 17 by each flexible duct 22. It is reduced by the silencer.

  In addition, about the other structure and effect | action of the noise reduction system which concern on 2nd Embodiment, since it is the same as that of 1st Embodiment, description is abbreviate | omitted.

  Thus, by providing a muffling member in the flexible duct, high frequency noise can be reduced.

<Experimental example>
In order to confirm the effect of the noise reduction system according to the first embodiment of the present invention, the noise reduction system provided with a soundproof sheet provided so as to cover the air compressor, the generator, and the ultrahigh pressure pump. The measurement result will be described.

  First, sound pressure levels as shown in FIG. 6 were measured at the upper portions of the engine exhaust ports of the air compressor, the generator, and the ultrahigh pressure pump.

  At this time, (1) the front of the speaker unit, (2) directly above the speaker unit, (3) the top of the soundproof panel, (4) diagonally forward of the speaker unit, and (5) the soundproof sheet on the side opposite to the speaker unit side. When the sound pressure level was measured at each of the upper portions, the measurement results as shown in FIG. 7 were obtained. It has been found that low frequency noise of 50 Hz to 80 Hz is reduced.

  In the above embodiment, a case where the construction machine is covered with the soundproof sheet has been described as an example. However, the present invention is not limited to this, and the construction machine is configured with a soundproof wall constituted by a soundproof panel or the like. You may make it cover.

  Moreover, although the case where the soundproof sheet and the soundproof wall are provided has been described as an example, a free sound field without the soundproof sheet and the soundproof wall may be used. For example, as shown in FIG. 8, you may make it arrange | position a speaker unit on the vehicle body of a heavy construction machine. In this case, the opening portion of the flexible duct may be disposed on the middle portion of the speaker unit on the vehicle body of the heavy construction equipment.

  Moreover, although the case where a flexible duct was used was demonstrated to the example, it is not limited to this, A duct other than a bellows-like flexible duct may be used if it is a duct which has flexibility.

  Further, the case where the noise source is the engine exhaust port of the construction machine has been described as an example, but the present invention is not limited to this, and noise from other noise sources may be reduced.

  Moreover, although the case where the speakers of the speaker unit are arranged in the left-right direction has been described as an example, the present invention is not limited to this, and the speakers may be arranged adjacent to each other in the direction other than the left-right direction. In this case, the openings of the plurality of flexible ducts may be arranged so as to be arranged in a direction orthogonal to the speaker arrangement direction.

DESCRIPTION OF SYMBOLS 10 Noise reduction system 12 Construction machine 12A Engine exhaust port 14 Soundproof sheet 14A Exhaust port 16 Speaker 17 Speaker unit 18 Error microphone 20 Noise reduction device 22 Flexible duct 42 Power amplifier 46 Inverse filter DSP
54 Inverse filter operation unit 58 Inverse filter

Claims (7)

A speaker unit that emits a control sound on the side opposite to a noise source disposed in a housing having an exhaust port, and includes a plurality of speakers disposed adjacent to each other;
A duct portion having openings at both ends, wherein an opening on one end side is provided at an exhaust port of the housing , and noise from the noise source is provided at an intermediate portion between the plurality of speakers of the speaker unit. A duct portion that leads to the opening on the other end side,
A microphone that collects noise on the side opposite to the noise source from the speaker unit, 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;
Input means for inputting the reduced signals generated by the generating means to the plurality of speakers;
Noise reduction device including   The noise reduction device according to claim 1, wherein the speaker unit is disposed in an opening portion provided as a soundproof sheet provided so as to cover the noise source or an exhaust port of a soundproof wall. The noise source is a plurality of noise sources,
The noise reduction device according to claim 1, wherein the duct portion is a plurality of duct portions provided for the plurality of noise sources. The noise sources are a plurality of noise sources having different noise frequencies,
The openings on the other end side of the plurality of duct portions are arranged in an intermediate portion between the plurality of speakers so as to be arranged in a direction orthogonal to the arrangement direction of the plurality of speakers,
The noise reduction device according to claim 3, wherein a noise source having a higher noise frequency is disposed closer to a line connecting the centers of the plurality of speakers.   The noise reduction device according to any one of claims 1 to 4, wherein a silencer member is provided inside the duct portion.   The noise reduction device according to claim 1, wherein the duct portion is a bellows-like flexible duct. The noise reduction device according to any one of claims 1 to 6,
A soundproof sheet or soundproof wall provided to cover the noise source, wherein the speaker unit is disposed in an opening provided as an exhaust port; and
Including noise reduction system.

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