JPH04240894A - Sound eliminator for radiated noise at opening part - Google Patents

Abstract

PURPOSE:To stably eliminate a noise radiated from the opening part of a sound insulation cover. CONSTITUTION:Error microphones 26 and 28 are classified into a 1st error microphone and a 2nd error microphone and the filter coefficient of an adaptive digital filter 36, 38 is updated by a controller. Namely, a filter coefficient for minimizing the output signal of the 1st error microphone is calculated at some sampling time according to only information regarding the 1st error microphone and the filter coefficient of the adaptive digital filter is updated with this filter coefficient. Then a filter coefficient for minimizing the output signal of the 2nd error microphones is calculated at next sampling time according to only information regarding the 2nd error microphone and the filter coefficient of the adaptive digital filter is updated with the calculated filter coefficient.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a silencing device for radiated noise from openings, and in particular for silencing noise radiated from openings such as ventilation holes formed in soundproof covers of construction buildings, entrances and exits for workers, etc. This invention relates to a silencing device for radiated noise from an opening.

0002

2. Description of the Related Art Conventionally, as shown in FIG. 3, in this type of noise damping device, sound absorbing pipes 3, 3 are installed in ventilation holes 2, 2 formed on both sides of a soundproof cover 1, respectively, and directed toward the outside of the soundproof cover 1. Installed. The sound absorbing pipes 3, 3 have sound absorbing materials 4, 4 made of porous material attached to their inner peripheral surfaces, and an outlet opening 5.
, 5 are curved downward in the figure.

[0003] As a result, among the noise radiated from the noise source 7 in the room 6, the noise propagated to the ventilation holes 5, 5 is
The sound is absorbed and muffled by the sound absorbing materials 4, 4. In addition, by lengthening or bending the sound absorbing tubes 3, 3, the sound deadening effect can be further improved. However, the sound damping device using the pipe structure has a drawback that it cannot be applied to mechanical equipment that emits low frequency noise because the sound absorbing material 4 itself has poor low frequency sound damping ability. Further, if the sound absorbing tube 3 is made longer, the muffling device becomes larger, and if the shape of the sound absorbing tube 3 is complicated, the pressure loss increases and the ventilation effect deteriorates.

On the other hand, as another noise muffling device for muffling the noise radiated to the outside from the opening 2,
There is an electronic muffling device that emits additional sound having an opposite phase and the same sound pressure to the noise from the noise source 7, and forcibly produces a muffling effect by the sound wave interference. With the rapid development of electronic devices, signal processing technology, etc., research results regarding this type of silencer have recently been published one after another from various viewpoints.

Regarding this silencing device, the applicant of the present application has already disclosed a system configuration for practical use in Japanese Patent Application No. 7115/1983. When such a system configuration is applied to the present silencer, a sensor microphone that detects noise from a noise source and an error microphone are installed on the upstream and downstream sides of the ventilation opening in the noise radiation direction with respect to the additional sound source (hereinafter referred to as the speaker). Install each on the side. The sensor microphone is installed indoors to prevent the soundproof cover from being affected by external noise, and the error microphone is similarly installed near the ventilation opening. Then, the sensor microphone, error microphone, and speaker are connected to the control device. The control device generates, based on signals from the sensor microphone and the error microphone, a drive signal for causing the speaker to generate additional sound having an opposite phase and the same sound pressure as the noise radiated to the outside from the ventilation port. create.

[0006] Since the system configuration of the present invention is based on the control of a one-dimensional sound field, the muffling band is capable of muffling up to a plane wave propagation frequency determined by the aperture of the ventilation opening. Regarding this, the applicant of the present application has disclosed
It has already been disclosed in the specification of Japanese Patent No. 400.

[0007]

[Problem to be Solved by the Invention] However, in conventional electronic silencers, when multiple speakers and error microphones are installed, in an unpaired system, the noise is input to the error microphone as second and third noise. , there is a drawback that the silencing accuracy deteriorates. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an aperture-radiated noise muffling device that can stably muffle noise emitted from an aperture over a wide range.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method for emitting noise from a noise source installed in a room surrounded by a soundproof cover from an opening formed in the soundproof cover. This is a silencing device for opening radiated noise, which generates a sound wave with the opposite phase and the same sound pressure as the propagating sound wave emitted from the noise source, and generates a sound wave at the plane of the opening and in the vicinity. A muffling device for aperture radiated noise that performs muffling by sound wave interference includes one or more noise information detecting means for detecting noise information of the noise source and converting it into an electrical signal, and detecting the propagating sound waves from the noise source. additional sound generating means for emitting additional sound for canceling in and near the opening plane; and installed on the opening plane to detect propagating sound waves from the noise source and additional sound from the additional sound generating means. a plurality of error microphones that convert the noise information into electrical signals; and an adaptive digital filter that captures the output signal of the noise information detection means and creates a drive signal to be transmitted to the additional sound generation means based on a given filter coefficient; Sampling the output signals from the noise information detection means and the plurality of error microphones, calculating filter coefficients for minimizing the output signals of the plurality of error microphones based on the sampled signals for each sampling, and calculating the filter coefficients for minimizing the output signals of the plurality of error microphones. control means for updating the filter coefficients of the adaptive digital filter with the coefficients; the additional sound generating means is installed so that the generation surfaces thereof face each other inside the opening; and the plurality of error microphones are arranged inside the opening. It is characterized by being installed on a flat surface.

[0009]

[Operation] According to the present invention, noting that the electronic silencing system is effective in reducing low-frequency noise, an experiment was conducted in which error microphones were installed at each position shown in Figure 4, and it was found that the plane of the opening has a large silencing effect. Check and install multiple error microphones on the opening plane. Then, these error microphones are divided into one or more first error microphones, one or more second error microphones, and so on. When sampling the noise information from the noise source and the output signals from the plurality of error microphones, the control device controls the output of the first error microphone based only on information related to the first error microphone at a certain sampling time. A filter coefficient for minimizing the signal is calculated, and the filter coefficient of the adaptive digital filter is updated with the calculated filter coefficient. At the time of the next sampling, a filter coefficient for minimizing the output signal of the second error microphone is calculated based only on the information related to the second error microphone, and the filter coefficient of the adaptive digital filter is calculated using the calculated filter coefficient. Update.

[0010] Therefore, by sequentially and repeatedly updating the filter coefficients for each sampling, it is possible to stably muffle the noise emitted from the opening over a wide range.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the silencing device for radiated noise from openings according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an embodiment of a silencing device for aperture radiated noise according to the present invention. As shown in FIG. 1, a machine tool 14 that is a source of noise is installed in a soundproof room 12 surrounded by a soundproof cover 10, and the soundproof cover 10 is used for ventilation of the soundproof room 12 and for transporting cargo. openings 16, 16 are formed on both sides thereof.

By the way, electronic silencers 18, 18 are installed in the openings 16, 16. The electronic silencer 18 includes a sensor microphone 24 and a pair of speakers 20, 2.
2. A pair of error microphones 26, 28 and controller 3
Consists of 0. The sensor microphone 24 detects noise propagated from the machine tool 14, converts the noise into an electrical signal, and outputs this electrical signal to the controller 30.

The pair of speakers 20 and 22 are arranged near the opening 16 on the side of the soundproof room 12, and are mounted so that their respective additional sound generating surfaces face toward the inside of the opening 16. The error microphones 26 and 28 are disposed on the plane of the opening 16, and detect the interference sound caused by the interference between the noise propagated from the machine tool 14 and the additional sound generated from the speakers 20 and 22. is converted into an electrical signal, and this electrical signal is output to the controller 30.

The controller 30 includes the sensor microphone 2
4 and error microphones 26, 28, a signal is created to minimize the output signals of the error microphones 26, 28, and this created signal is transmitted to the speaker 2.
It is output to 0 and 22. Next, a method of controlling the controller 30 of the aperture radiated noise muffling device configured as described above will be described with reference to FIG. 3.

First, when the sensor microphone 24 detects noise from the machine tool 14, the sensor microphone 24 converts the noise into an electrical signal, and this electrical signal is sent via the amplifier 32 and A/D converter 34 of the controller 30. and outputs to adaptive digital filters 36, 38 and control units 40, 42. At approximately the same time, when the error microphones 26 and 28 detect the interference sound, the error microphones 26 and 28 convert the interference sound into an electrical signal, and this electrical signal is sent to the controller 30.
The signals are output to the control sections 40 and 42 via amplifiers 44 and 46 and A/D converters 48 and 50, respectively.

Next, when the control units 40 and 42 receive the respective electric signals from the sensor microphone 24 and the error microphones 26 and 28, they calculate filter coefficients W1 and W2 for each sampling, and calculate the filter coefficients W1 and W2 for each sampling. W1, W2
The filter coefficients of the adaptive digital filters 36 and 38 described above are updated. Then, the updated filter coefficients are applied to the D/A converters 52, 52 and the amplifiers 54, 54.
The signal is output to the speakers 20 and 22 via.

Note that the control sections 40 and 42 each include reference signal calculation sections 56 and 58 and an execution section 60. Further, the reference signal calculation section 56,
58 are speakers 20, 22 and error microphone 26, respectively.
, 28 transfer functions C1, C2, C3
, C4.

According to the reference signal calculation units 56 and 58 configured as described above, a signal indicating noise sampled sequentially at a predetermined period, that is, a signal indicating X in the figure, and filter coefficients C1, C2, C3, A convolution operation is performed using C4. Then, a reference signal is created and this reference signal is output to the execution units 60, 60. As explained above, in this embodiment, when electric signals are received from the sensor microphone 24 and the error microphones 26 and 28,
Calculate filter coefficients W1 and W2 for each sampling,
Since the filter coefficients of the adaptive digital filters 36 and 38 are updated using the filter coefficients W1 and W2, the transfer functions of all systems between the speakers 20 and 22 and the error microphones 26 and 28 can be covered. .

Therefore, according to this embodiment, it is possible to obtain a stable silencing effect over a wide range, compared to the conventional silencing device for radiated noise from an opening. Note that the filter coefficient C1 is fixed in advance so that the output of the FIR digital filter that drives the speakers 20 and 22 with a pseudo-random signal and inputs this pseudo-random signal matches the error output of the error microphones 26 and 28. There is. Furthermore, filter coefficients C2, C3, and C4 are similarly fixed.

Furthermore, in this embodiment, a sensor microphone is used as the noise information detection means, but the invention is not limited to this. If the noise source is periodic, vibrations from a mechanical device can be used as an electrical signal. A vibration pickup sensor for input may also be used. Further, in this embodiment, error microphones are classified one by one, but a plurality of error microphones may be classified.

[0021]

As explained above, according to the silencing device for aperture radiated noise according to the present invention, one or more first error microphones, one or more second error microphones, and one or more second error microphones can be used. error microphone..., and a control device calculates a filter coefficient for minimizing the output signal of the first error microphone based only on information related to the first error microphone at a certain sampling time. , to update the filter coefficient of the adaptive digital filter with the calculated filter coefficient, and to minimize the output signal of the second error microphone based only on the information related to the second error microphone at the next sampling time. Since the filter coefficients of the adaptive digital filter are updated with the calculated filter coefficients, it is possible to stably muffle the noise emitted from the opening over a wide range.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the silencing device for opening radiated noise according to the present invention.

[Fig. 2] System configuration diagram of the silencing device for opening radiated noise according to the present invention

[Fig. 3] An explanatory diagram showing an example of a conventional silencing device for radiated noise from an opening.

FIG. 4 is an explanatory diagram showing an embodiment of the silencing device for radiated noise from an opening according to the present invention, in which a plurality of error microphones are installed in the opening.

[Explanation of symbols]

20, 22...Speaker 24...Sensor microphone 26, 28...Error microphone 30...Controller 36, 38...Adaptive digital filter 40, 42...Control unit 56, 58...Reference signal calculation unit

Claims (1)

[Claims] [Claim 1] A silencing device for opening radiated noise, which muffles noise emitted from an opening formed in a soundproof cover among noise from a noise source installed in a room surrounded by a soundproof cover, , in a silencing device for opening radiated noise, which generates a sound wave having the opposite phase and the same sound pressure as the propagating sound wave emitted from the noise source, and muffling the noise by the sound wave interference in and near the opening plane. , one or more noise information detection means for detecting noise information of the noise source and converting it into an electrical signal, and emitting additional sound for canceling the propagating sound waves from the noise source in and near the opening plane. a plurality of error microphones provided on and near the opening plane to detect propagating sound waves from the noise source and additional sound from the additional sound generating means and converting them into electrical signals; an adaptive digital filter that takes in the output signal of the noise information detection means and creates a drive signal to be sent to the additional sound generation means based on a given filter coefficient; Sampling the output signal, calculating filter coefficients for minimizing the output signals of the plurality of error microphones based on the sampled signal for each sampling, and using the filter coefficients to set the filter coefficients of the adaptive digital filter. and a control means for updating, the additional sound generating means being installed inside the opening so that generation surfaces thereof face each other, and the plurality of error microphones being provided on the plane of the opening. Silencer for radiated noise