JPH0342999A - Silencing device for radiation noise in opening section - Google Patents

Abstract

PURPOSE:To realize a radiation noise silencer in an opening section not hindering the passing of a person or a commodity by generating an additional sound having opposite phase and the same sound pressure to a noise radiating from an opening section based on a signal from a noise information detection means and an error microphone. CONSTITUTION:A sensor microphone SM is arranged to the intake side of a ventilation port 14 and detects a noise radiating from a machine 10 via the ventilation port 14 and outputs its detection signal to a controller 20. A speaker S is arranged in the vicinity of the outlet of the ventilation port 14 and generates additional sound to cancel the noise radiating from the ventilation port 14 with a driving signal from the controller 20. An error microphone EM is arranged to a prescribed position in a direction where the noise radiates from the ventilation port 14, detects a sound wave after the additional sound from the speaker S and the noise are interfered with each other and outputs its detection signal (error signal) to the controller 20. The controller 20 outputs a signal with a prescribed amplitude and phase characteristic to the speaker S radiating the silencing sound wave so as to minimize the error signal E.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a silencing device for radiating noise from openings, and in particular, the present invention relates to a silencing device for radiating noise from openings, and in particular from openings such as ventilation holes provided in the walls of factory buildings, entrances and exits for people, etc. The present invention relates to a silencing device for aperture radiated noise that mutes noise.

[Conventional technology]

Conventionally, this type of silencer has been comprised of a duct 4 extending from a ventilation opening 2 and a sound absorbing material 6 lined inside the duct 4, as shown in FIG.

[Problem to be solved by the invention]

However, the above-mentioned conventional sound damping device was not very effective even when applied to a factory building where machinery and equipment that emit low-frequency noise were installed, because the sound-absorbing material 6 itself had poor low-frequency sound absorption ability. . In addition, in order to increase the noise reduction effect, there are some models in which the duct 4 is bent into an appropriate shape, but in that case, pressure loss increases, ventilation efficiency decreases, and the duct becomes larger, making it difficult to install the IT itself. There were problems such as increased space.

Furthermore, in the case of such a silencer, there is a problem that it cannot be installed at an entrance/exit (opening) through which people and goods pass.

The present invention was made in view of these circumstances, and is effective in muffling low-frequency noise, with little pressure loss, and is safe for people and
It is an object of the present invention to provide a silencing device for radiated noise from an opening that does not obstruct the passage of articles etc. a noise information detection means for detecting information on noise radiated through the provided opening; and a noise information detection means disposed near the opening to generate additional sound for canceling the noise radiated from the opening. Additional sound generating means is disposed at a predetermined position in the direction in which noise is radiated from the opening, and after the noise radiated from the opening and the additional sound generated from the additional sound generating means cause sonic interference. an error microphone that detects a sound wave; and an error microphone that generates an additional sound having an opposite phase and the same sound pressure as the noise radiated from the opening, based on signals from the noise information detection means and the error microphone. The invention is characterized by comprising a control means for creating a drive signal to be generated from the means.

[Effect]

The present invention is an active silencing device, that is, an electronic silencing system that radiates additional sound of the same sound pressure and opposite phase to the noise propagating from the noise source, and forcibly produces a silencing effect by sonic interference. After confirming that it is effective against frequency noise, the additional sound generated from the additional sound generating means, which is one of the components of the electronic silencing system, interferes with the noise radiated from the opening in the wall. The sound generating means is arranged near the opening. Furthermore, an error microphone for evaluating the silencing effect is also placed at a predetermined position in the direction in which noise is radiated from the opening.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the silencing device for aperture radiated noise according to the present invention will be described in detail below with reference to the accompanying drawings.

In FIG. 1, a machine 10, which is a source of noise, is surrounded by a soundproof cover 12. This soundproof cover 12
A ventilation opening 14 is provided on the wall of the room, and a ventilation fan 16 is attached to the ventilation opening 14.

The silencing device for opening radiated noise according to the present invention is for silencing the noise radiated from the ventilation port 14 to the outside of the soundproof cover 12, and mainly includes a sensor microphone SM as a noise information detecting means and an additional sound generating means. Speaker S as
It is comprised of an error microphone EM for evaluating the silencing effect, and a control device 20 that outputs a drive signal to the speaker S based on the output signals of the sensor microphone SM and the error microphone EM.

The sensor microphone SM is arranged on the entrance side of the ventilation port 14,
Noise emitted from the machine 10 through the ventilation port 14 is detected, and a detection signal thereof is output to the control device 20.

The speaker S is arranged near the outlet of the ventilation port 14, and
The Ill signal from the device 20 generates additional sound to cancel out the noise emitted from the ventilation port 14.

The error microphone EM is arranged at a predetermined position in the direction in which noise is radiated from the ventilation port 14, detects the sound waves after the noise and the additional sound from the speaker S interfere with each other, and outputs the detection signal (error signal). Control! It is output to the II device 20.

FIG. 2 is a block diagram showing an embodiment of the control device 20, in which a signal X indicating noise detected by the sensor microphone SM and outputted via the amplifier 21 and the A/D converter 22 is applied to the FIR. The signal is input to a type digital filter 23 and a controller section 24. Also, controller l 241. :l: The output signal of the error microphone EM is input as the vanilla signal E via the amplifier 25 and the A/D converter 26.

The controller unit 24 determines a transfer function to be given to the digital filter 23 based on the input signal is applied to the digital filter 23. The digital filter 23 converts the human signal X into a signal with predetermined amplitude and phase characteristics based on the given filter coefficients.

The output signal of this digital filter 23 is D/A converted by a D/A converter 27 and output to a speaker S that emits sound waves for silencing. In this way, the propagating sound waves from the noise source are canceled at the position of the error microphone EM.

The important problem here is that the transfer function is accompanied by a delay in the electrical system including the amplifier and the speaker, and a delay in the time when the sound wave reaches the error microphone EM from the speaker S.

This is taken into consideration by the FIR digital filter in the controller section 24.

Further, the transfer function at the start of control is created in advance using a pseudo signal, and the control device 20 is equipped with pseudo signal generating means (not shown).

That is, before operating the system, a pseudo signal is output to the speaker S to radiate a sound wave to the sound wave propagation region, and a transfer function is specified based on the output signal of the error microphone EM so that the output signal is minimized. , in consideration of the specified transfer function, filter coefficients that specify the transfer function to be applied to the digital filter 23 are determined based on a predetermined adaptive algorithm.

When the system is in operation, the filter coefficients are fixed and the digital filter 23 is adaptively controlled by the VS-LMS algorithm.

In the above embodiment, the control device 20 has been explained collectively, but as shown in FIG. A plurality of control devices 20a to 20d may be provided.

Further, FIGS. 4 and 5 each show other examples of speaker arrangement, and the speaker S shown in FIG. The speaker S shown in FIG. 4 is placed apart from the ventilation port 14.

Furthermore, in this embodiment, the case where the silencer is installed in the ventilation hole is explained, but this is not limited to this, and as shown in FIG. The silencer of the present invention is disposed in an opening in a wall that partitions the
Noise radiated to areas where people are present may be muted.

〔Effect of the invention〕

As explained above, according to the silencing device for radiated noise from openings according to the present invention, it is possible to muffle the noise radiated from openings such as ventilation holes provided in walls and entrances and exits for people. It can be expected to have a great effect on low-frequency noise that cannot be completely removed.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing one embodiment of the silencing device for opening radiated noise according to the present invention, FIG. 2 is a block diagram showing an example of the configuration of the control device shown in FIG. 1, and FIG. 3 is a block diagram showing a configuration example of the control device shown in FIG. FIGS. 4 and 5 are diagrams showing other examples of speaker arrangement, respectively. FIG. FIG. 7 is a diagram showing an example of a conventional muffling device. DESCRIPTION OF SYMBOLS 10... Noise source (machine), 12... Soundproof cover 14... Ventilation opening, 20.20a-20d... Control device, 22.26... A/D converter, 23...
FIR adaptive digital filter, 24... Controller section, 26... A/D converter, SM...
Sensor microphone, S, S, ~S,...Speaker, EM...Error microphone.

Claims (1)

[Scope of Claims] Noise information detection means for detecting information on noise emitted from a noise source through an opening provided in a wall; an additional sound generating means for generating additional sound to cancel the noise generated by the opening; and an additional sound generating means disposed at a predetermined position in the direction in which the noise is radiated from the opening, the noise radiated from the opening and the additional sound generating means. an error microphone that detects the sound waves after the generated additional sound has caused sonic interference; and an error microphone that is in opposite phase to the noise radiated from the opening and based on signals from the noise information detection means and the error microphone. A silencing device for opening radiated noise, comprising: a control means for creating a drive signal for causing the additional sound generation means to generate additional sound of the same sound pressure.