JPH06266368A - Acoustic intensity type sound elimination device - Google Patents

Abstract

PURPOSE:To obtain the acoustic intensity type sound elimination device which eliminates a sound with higher directivity. CONSTITUTION:Plural acoustic intensity detecting means 14 of the acoustic intensity type sound elimination device are provided in a space, where sound elimination is performed at different positions, facing a sound source and a reference signal detecting means 13 is also provided facing the sound source, and, a signal processor controls control sounds from plural actuators 24 for sound elimination according to the outputs of the acoustic intensity detecting means 14 and the reference signal from the reference signal detecting means 13 so that a noise is minimized at the setting positions of the acoustic intensity detecting means 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound intensity type silencer for silencing noise from a noise source.

[0002]

2. Description of the Related Art A muffler is based on the idea that if sound waves having the same waveform and the same amplitude as a sound wave propagating from a noise source are emitted with opposite phases, the sound waves interfere with each other and cancel each other out. . The conventional device has, as basic constituent elements, a reference signal detecting unit for detecting a reference signal from a noise source, a silencing actuator that emits a control sound in a space where noise from the noise source is propagated, and a noise level in the space. And a signal processing device for controlling the noise reduction actuator based on the reference signal detected by the reference signal detection unit and the noise level detected by the noise information detection unit.

Japanese Unexamined Patent Publication No. 3-203494 proposes a device which uses, as noise information detecting means, sound intensity detecting means for capturing sounds in space as vector quantities. The signal processing device controls the muffling actuator based on the detected intensity and the reference signal.
According to this device, not only the loudness of the sound in the space but also the direction thereof is detected, so that it is possible to remove the noise with higher directivity. That is, it is possible to minimize the noise level at the installation position of the sound intensity detecting means.

However, in the conventional sound intensity type silencer, when there are a plurality of noise sources, it is possible to muffle the mixed noise of the plurality of noise sources, but only the sound of a particular noise source is generated. I couldn't silence it. That is, it is difficult to give the directivity of the noise source to be silenced. In addition, if the conventional sound intensity type silencer is used for silencing a wider space, the output of one silencing actuator will have a great effect on the acoustic intensity at a plurality of points, and the silencing effect can be obtained. It gets harder.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sound intensity silencer with a high directivity to a noise source to be silenced, that is, when there are a plurality of noise sources, one or more specific noise sources. It is an object of the present invention to obtain a device capable of selectively removing only the noise of.

[0006]

SUMMARY OF THE INVENTION The present invention provides a plurality of sound intensity detecting means in a sound intensity silencer at different positions in a space to be silenced and toward a noise source, and a sound deadening actuator, A plurality of different positions are provided in the space, and a control sound from the plurality of muffling actuators is controlled by the signal processing device according to the outputs of the plurality of sound intensity detecting means and the reference signal. It is characterized by controlling so that the noise is minimized at the set position of the detection means. The reference signal detecting means is preferably composed of a directional microphone directed to the noise source. By using this directional microphone and the outputs of the plurality of intensity detecting means for the noise source, the sound of the noise source can be more effectively silenced. That is, it is possible to selectively mute only the sound of the noise source to which the directional microphone and the plurality of intensity detecting means are directed with high directivity.

As the sound intensity detecting means, specifically, a means for detecting the instantaneous sound pressure of sound and the particle velocity is known. The signal processing device sets different transfer functions for the instantaneous sound pressure and the particle velocity by each acoustic intensity detecting means based on the difference in the sound transmitting path between the plurality of acoustic intensity detecting means and the plurality of sound deadening actuators. As a result, the muffling actuator is operated so that the noise level at the installation position of each sound intensity detecting means is minimized.

[0008]

The present invention will be described below with reference to the illustrated embodiments.
In this embodiment, a noise source 12 is assumed at one end of a large duct 11 having a rectangular cross section schematically shown in FIG. A directional microphone 13 is provided in the vicinity of the noise source 12 as a reference signal detecting means for detecting the reference signal x from the noise source 12. The directional microphone 13 is directed toward the noise source 12 and detects only the sound of the noise source 12. On the other hand, four acoustic intensity detection probes (AI probes) 14 are arranged at the other end of the large duct 11. In the illustrated example, the four AI probes 14 are
Although it is arranged in a plane orthogonal to the longitudinal direction of, that is, in a plane orthogonal to the propagation direction of the sound from the noise source 12, it is not always necessary.

Each of the AI probes 14 is directed to the noise source 12 in order to detect the sound intensity as a vector amount from the noise source 12. That is, each AI probe 14 is provided with a pair of sensor microphones 14a and 14b that are separated by a certain distance in the propagation direction of the sound from the noise source 12, and the output of each sensor microphone 14a and 14b will be described in detail in FIG. Sound intensity calculation circuit 15 shown
Are input respectively.

As shown in FIG. 2, the sensor microphone 14a,
The outputs of 14b are amplifiers 16a, 16b, A /
D converters 17a and 17b, and band pass filter 18
It is input to the adder 19 and the subtractor 20 via a and 18b. The output from the adder 19 is subjected to block adaptation processing by the block processing circuit 21a, and is taken out as the instantaneous sound pressure p. Also, the subtractor 20
The output that has passed is subjected to block adaptive processing by the block processing circuit 21b after being integrated by the integrator 22, and is extracted as the particle velocity u. The sound intensity as a vector quantity is calculated by the instantaneous sound pressure p and the particle velocity u.
Represented by This is already well known.

In the large duct 11, the noise source 12 and the AI
Positioned between the probes 14, four speakers 24 are arranged as muffling actuators. The four speakers 24 are four AI probes 1 in the illustrated example.
Like No. 4, it is arranged in a plane orthogonal to the longitudinal direction of the large duct 11, that is, in a plane orthogonal to the propagation direction of the sound from the noise source 12, but it is not always necessary.

The silencer of the present invention basically comprises four AI probes 14 and an acoustic intensity calculation circuit 15.
The noise intensity (instantaneous sound pressure p and particle velocity u) detected by the reference signal x and the reference signal x of the noise source 12 detected by the directional microphone 13 are input to the signal processing device 30, and the amplifiers 26 are input. Through the four speakers 24 so that the noise level at the installation point of the AI probe 14, that is, the sound intensity is minimized.
Is to drive.

The control system of the present invention will be described in more detail with reference to FIGS. 3 and 4. As shown in FIG. 3, four A's
Instantaneous sound pressures p _{1 to} p at each point obtained by the I probe 14 and the sound intensity calculation circuit 15, respectively.
₄ and particle velocities u _{1 to} u ₄ are respectively measured by the signal processing device 3
It is input to the signal processor 31 in 0. On the other hand, the reference signal x from the directional microphone 13 is the A / D converter 32.
And the signal processor 3 via the adaptive filter 33.
Input to 1. The signal processor 31 receives the input of the instantaneous sound pressure p, the particle velocity u and the reference signal x, updates the filter coefficient of the adaptive filter (phase reversal filter) 34 thereof at every predetermined minute time, and outputs the signal y ₁ Each speaker 24 is driven based on ~ y ₄ .

Each speaker 24 and each sensor microphone 14
As shown in FIG. 4, different transfer functions are set between a and 14b for the instantaneous sound pressures p _{1 to} p ₄ and the particle velocities u _{1 to} u ₄ , respectively, based on the difference in the transfer paths. As shown in the figure, these transfer functions are C _P11 , C _U11 ~
32 _types (4 × 8) of C _P44 and C _U44 are set. Based on this transfer function, the adaptive filter group C hat
The filter coefficients of _P11 , C hat _{U11 to} C hat _P44 , C hat _U44 are set. “C hat” means a character in which “∧” is drawn on the character “C” in FIG. 4, and this adaptive filter group means a filter according to a transfer function. The signal processing device 30 drives the adaptive filter 34 according to these filter outputs, and outputs drive signals y _{1 to} y ₄ to each speaker 24. The control loop controls the speaker 24 so that the noise intensity in the installation plane of the AI probe 14 is minimized.

According to the above configuration, especially the noise of the noise source 12 can be effectively silenced. For example, considering the case where another noise source 12a exists in the large duct 11, when the directional microphone 12 and the four AI probes 14 are all directed toward the noise source 12, only the sound of the noise source 12 is selectively selected. When the sound source 12a is directed to the noise source 12a, only the sound of the noise source 12a can be selectively muted. This effect is very effective when only the sound of the noise source 12a is desired to be heard separately from the noise source 12, or vice versa.

Although the present invention has been described above by taking the muffling device in the large duct 11 as an example, it is obvious that the muffling device of the present invention can be used for silencing any silencing space other than the duct. is there.

[0017]

As described above, according to the present invention, it is possible to muffle the noise of a specific noise source with high directivity.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an embodiment of a sound intensity type silencer according to the present invention.

FIG. 2 is a block diagram showing a specific example of a sound intensity calculation circuit by one sound intensity detecting means in the device of FIG.

3 is a block diagram showing a specific example of a signal processing circuit of the apparatus of FIG.

FIG. 4 is a connection diagram schematically showing a setting state of a transfer function based on path differences between a plurality of sound intensity detecting means and a plurality of sound deadening actuators.

[Explanation of symbols]

 11 Large Duct (Silent Space) 12 Noise Source 13 Directional Microphone (Reference Signal Detecting Means) 14 AI Probe (Sound Intensity Detecting Means) 15 Sound Intensity Arithmetic Circuit 24 Speaker (Muffing Actuator) 30 Signal Processor 33 Adaptive Filter 34 Adaptive filter (phase inversion filter)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H03H 21/00 7037-5J

Claims (4)

[Claims] 1. A reference signal detecting means for detecting a reference signal from a noise source; a silencing actuator for producing a control sound in a space in which noise from the noise source propagates; a vector amount of the sound in the space. Sound intensity detecting means for detecting the sound intensity as a signal; a signal for controlling the silencing actuator based on the reference signal detected by the reference signal detecting means and the sound intensity detected by the sound intensity detecting means. In a sound intensity type silencer including a processing device, a plurality of the sound intensity detecting means are provided at different positions in the space and toward the noise source, and the sound deadening actuator is A plurality of different positions are provided in the space, and in the above signal processing device, control from the muffling actuator is performed. A sound intensity type silencer characterized by controlling sound according to outputs of the plurality of sound intensity detecting means and a reference signal so that noise is minimized at a set position of the sound intensity detecting means. . 2. The sound intensity silencer according to claim 1, wherein the reference signal detecting means is a directional microphone directed to a noise source. 3. The sound intensity detecting means according to claim 1 or 2, wherein the sound intensity detecting means detects the instantaneous sound pressure and the particle velocity of the sound, and the signal processing device comprises a plurality of sound intensity detecting means and a plurality of sound intensity detecting means. The sound intensity silencer that sets different transfer functions for the instantaneous sound pressure and the particle velocity by each sound intensity detecting means based on the difference in the sound transmission path from the sound deadening actuator. 4. The sound intensity according to claim 1, wherein each intensity detecting means is a pair of sensor microphones arranged at a certain distance in a sound propagation direction from a noise source. Type silencer.