JPH06295183A - Noise controller - Google Patents

Abstract

PURPOSE:To prevent the dispersion of a noise reduction effect amount from occurring in space in a noise controller eliminating the noise by outputting a signal having a phase opposite to and sound pressure equal to the noise from the muffler of an automobile from a speaker. CONSTITUTION:The noise controller arranged in the vicinity of the outlet of a tail pipe 2 emitting the noise with the end pipe of the muffler 1 eliminating the whirr of the exhaust of the automobile and canceling the noise from the tail pipe 2 is provided with an actuator 20 outputting an eliminating sound having the phase opposite to and the sound pressure equal to the noise of the tail pipe 2, microphones 5-1, 5-2, 5-3, set up respectively at least in the vicinity position of the actuator, on the position separated from the actuator 20 by a fixed distance and on the position of the rear side of the actuator 20 where the leakage noise exists and a synthesis circuit 6-10 synthesizing the outputs of the microphones based on the contribution degrees of the microphones 5-1, 5-2, 5-3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise control device for canceling noise from a muffler of an automobile and outputting a signal having an anti-phase equal sound pressure from a speaker. The purpose is to prevent variations in quantity.

[0002]

2. Description of the Related Art Conventionally, a passive muffler such as a muffler has been used to reduce noise generated from an internal combustion engine, etc., but improvements have been made in terms of size, muffling characteristics and the like. On the other hand, the noise generated from the sound source and the opposite phase
An active noise control device has been proposed which outputs a compensation sound of equal sound pressure from a speaker to cancel noise. By the way, the frequency characteristic or stability of the active noise control device itself is not sufficient, and its practical application has been delayed. However, as a result of the recent development of signal processing technology using digital circuits and expansion of the frequency range to be handled, many practical noise control devices have been proposed (for example, Japanese Patent Laid-Open No. 63-311396).

This is because a noise source microphone installed upstream of the duct detects the noise, and a signal processing circuit outputs a signal having a phase opposite to that of the noise and equal sound pressure from a speaker installed downstream of the duct. It is a so-called two-microphone / one-speaker type active noise control device in which a feedback system for detecting and feeding back by a microphone for a sound deadening point is combined with a feed-forward system.

[0004]

By the way, in the conventional noise control device, since it is preferable that the noise is silenced at the place where the speaker is installed, the microphone for detecting the silenced result is provided in the vicinity of the speaker. It was being done.
However, since it is provided only in the vicinity, information on the residual noise output from the microphone cannot be obtained at a location away from the muffler, so the amount of silencing is not always uniform, and the silencing effect is not effective in a part of the space. There was a problem that there was a bias.

Therefore, in view of the above problems, it is an object of the present invention to provide a noise control device in which the effect of silencing is less locally biased.

[0006]

In order to solve the above-mentioned problems, the present invention is arranged near the exit of a tail pipe that emits noise at the end pipe of a muffler that suppresses the detoning noise of the exhaust gas of an automobile. An actuator, a plurality of microphones, and a synthesizing circuit are provided in a noise control device that eliminates the noise of.

The actuator outputs an erasing sound having a sound pressure opposite in phase to the noise of the tail pipe. The plurality of microphones are respectively installed at least in the vicinity of the actuator, at a position separated from the actuator by a certain distance, and at the position on the back side of the actuator where leaked noise exists.

The synthesizing circuit synthesizes the outputs of the plurality of microphones based on the silencing contributions of the plurality of microphones.

[0009]

According to the noise control device of the present invention, the actuator outputs the erasing sound having an equal phase antiphase with the noise of the tail pipe. The microphones are installed at least at positions in the vicinity of the actuator, at a certain distance from the actuator, and at the position on the back side of the actuator where leaked noise exists, and the residual sound in each part of the automobile is measured. The outputs are combined by the combining circuit based on the silencing contributions of the plurality of microphones, and the adaptive filter forms a compensation signal based on the combined signal. That is, by averaging the sensor inputs of the erasing points by synthesizing and synthesizing multiple points, the muffling effect can be obtained not only in the vicinity of the tail pipe but also in a distant place, and the unevenness of the muffling effect in the entire vehicle can be prevented and uniform. You can get a good muffling effect.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a noise control device which is a premise of an embodiment of the present invention. The noise control device shown in this figure includes an actuator 20 that eliminates noise emitted from a tail pipe 2 that is a terminal pipe of a muffler 1 that eliminates the explosion noise of an automobile exhaust, a noise from the tail pipe 2, the noise, and the actuator. Three microphones 5-1 and 5- arranged to supplement residual noise with the elimination sound of the anti-phase equal sound pressure emitted from 20 as an error signal and to be described later.
2 and 5-3 and a signal to the actuator 20 are converted from a digital signal to an analog signal or amplified, and an analog signal from the microphones 5-1, 5-2 and 5-2 is converted to a digital signal. FIR (Finite) that inputs and reproduces a reproduced noise signal, which will be described later, as a controlled signal and forms and outputs a compensating sound that eliminates noise through the interface 6.
Impulse Response), and a coefficient updating means for inputting a combined signal of error signals from the microphones 5-1, 5-2 and 5-3 to update the FIR filter coefficient of the adaptive filter 7. 8 and the output of the adaptive filter 7 to normalize the filter coefficient of the coefficient updating means 8 and the interface 6, actuator 20, microphone 5
1, 5-2 and 5-3, the first transfer characteristic simulating means 9 simulating the transfer characteristics up to the coefficient updating means 8 and the compensation signal of the adaptive filter 7 are inputted, and the transfer characteristic simulating means 9 is inputted.
Second transfer characteristic simulating means 10 having the same transfer characteristic simulating means 8 as described above, and the second transfer characteristic simulating means 1
0 output signal and microphones 5-1, 5-2 and 5-
A difference signal calculating means 11 for calculating a difference signal between the output signal of No. 3 and the combined signal and forming this difference signal as a reproduced noise signal to the adaptive filter 7 and the first transfer characteristic simulating means 9.
Including and The adaptive filter 7, the coefficient updating means 8, the first transfer characteristic simulating means 9, the second transfer characteristic simulating means 10 and the difference signal calculating means 11 are constituted by a digital signal processor (DSP).

The actuator 20 includes two speakers 3 and 4, an enclosure 21 that seals the rear portions of the two speakers 3 and 4, and a muffled sound emitted from the front surfaces of the two speakers 3 and 4 of the tail pipe 2. It consists of an erasing sound guide section 22 leading to the exit. FIG. 2 is a diagram showing the arrangement of the microphones of FIG. As shown in FIGS. 3A and 3B, in the rear partial view of the automobile as viewed from above or from the front, the first microphone 5-1 is installed at the outlet of the tail pipe 2 and is similar to a conventional installation place. . The second microphone 5-2 is installed at a position of about 1 m in the opposite lateral direction from the first microphone 5-1. Furthermore the third
The microphone 5-3 is installed between the actuator 20 and the muffler 1 due to noise that leaks from the space generated between the tail pipe 2 and the erase sound guide portion 22 and turns around. The above microphones 5-1, 5-2 and 5-3
The above arrangement is an example, and it may be provided in various places.

FIG. 3 is a diagram showing a circuit for synthesizing microphone outputs. The synthesizing circuit 6-10 shown in this figure includes an adding circuit 6-11 for adding signals from the microphones 5-1, 5-2 and 5-3, and an inverting circuit 6 for inverting the output of the adding circuit 6-11. -12 and the adder circuit 6-11
Adjust the resistors R1, R2 and R3 of the microphone 5
-1, 5-2 and 5-3, and a combination adjusting means 6-13 for changing the combination ratio of the outputs. The synthesis adjusting means 6-1
3 is initially adjusted to change the resistance values of the resistors R1, R2, and R3 of the adder circuit according to the degree of contribution of silencing the noise of the microphones 5-1, 5-2, and 5-3. Signals Sm1 and Sm from the microphones 5-1, 5-2 and 5-3
2, Sm3 is combined and output as Sm.

The transfer characteristic Hd1 of the first transfer characteristic simulating means 9 and the second transfer characteristic simulating means 10 is determined as follows. Stop the noise emission from the tail pipe 2,
Instead of the adaptive filter 7, white noise is output from that position, and the actuator 20, the interface 6,
Via the microphones 5-1, 5-2 and 5-3 and the interface 6, the transfer characteristic Hd1 of the second transfer characteristic simulating means 10 is set so that the output signal of the difference signal calculating means 11 becomes zero.
To determine Hd1 thus obtained as the first
Transfer characteristic simulating means 9 and second transfer characteristic simulating means 10
Set to.

In the coefficient updating means 8, the FIR filter coefficient (Ck (n); k: number of stages) of the adaptive filter 7 is obtained from the following equation by the least square method. Ck (n) = Ck (n-1) + (Sm (n) · α) / q (n + k-1) (1) where α is the convergence coefficient and Sm (n) is the microphone 5-
The composite signal of 1, 5-2 and 5-3, q (n + k-1) is the normalized signal from the first transfer characteristic simulating means 9, and n is the ordinal number of the digital signal.

A series of operations of the above noise control device will be described. The average transfer characteristic Hd from the output of the adaptive filter 7 to the microphone 5 and the average transfer characteristic Hm from the microphones 5-1, 5-2 and 5-3 to the filter coefficient updating means 8 are set from the tail pipe 2 as a noise source. Let Hnoise be the average transfer characteristic up to the microphones 5-1, 5-2 and 5-3. The average transfer characteristics Hd, Hm,
Hnoise is for each microphone 5-1, 5-2 and 5-
The transfer characteristics Hd, Hm, and Hnoise of No. 3 may be obtained by weighting the contribution of silencing the noises of the microphones 5-1, 5-2, and 5-3. Further, the noise signal from the tail pipe 2 is Sn, the output signals from the microphones 5-1, 5-2 and 5-3 are Sm1, Sm2 and Sm3, the compensation signal from the adaptive filter 7 is Sc, and the microphone 5 If the input signal Sm of the coefficient updating means 8 which is the combined output from -1, 5-2 and 5-3 and the output signal of the difference signal calculating means 11 are Se, the first transfer characteristic simulating means 9 and the second The transfer characteristic Tm1 simulated by the transfer characteristic simulating means 10 is: Tm1 = Hd.Hm (2), and the signal Sm0 detected by the microphones 5-1, 5-2 and 5-3 is as follows.

Sm0 = Sn.Hnoise + Sc.Hd (3) The noise reproduction signal which is the input signal of the adaptive filter 7 and the like, and the difference signal Se which is the calculation result in the difference signal calculating means 125 is From the above equations (2) and (3), it is obtained as follows. Se = Sm0.Hm-SC.Hd1 = (Sn.Hnoise + Sc.Hd) .Hm-SC.Hd.Hm = (Sn.Hnoise + Sc.Hd-SC.Hd) .Hm = Sn.Hnoise.Hm (4) ) Is formed as.

The input signal Sm of the coefficient updating means 8 is Sm = Hm.Sm0 (5), and the adaptive filter 7 changes the filter coefficient so that the input signal Sm becomes zero. The compensation signal Sc, which is the output signal of the filter 7, is Sm =
0, that is, Sm0 = 0, is determined from the above equation (2) as follows.

Sc ≈−Sn · Hnoise / Hd (5)

[0019]

As described above, according to the present invention, a plurality of microphones are respectively installed at a position near the actuator, a position separated from the actuator by a certain distance, a position on the back side of the actuator where leaked noise exists, and the like. Then, the residual sound in each part of the automobile is measured, and the output is combined based on the muffling contribution of each microphone to form a compensating signal to muffle the noise. The sound deadening effect can be obtained even in a place, the bias of the sound deadening effect in the entire vehicle can be prevented, and a uniform sound deadening effect can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a noise control device which is a premise of an embodiment of the present invention.

FIG. 2 is a diagram showing an arrangement of the microphones in FIG.

FIG. 3 is a diagram showing a circuit for synthesizing microphone outputs.

[Explanation of symbols]

 1 ... Muffler 2 ... Tail pipe 3, 4 ... Speakers 5-1, 5-2, 5-35 ... Microphone 6 ... Interface 6-1 ... Synthesis circuit 7 ... Adaptive filter 20 ... Actuator

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[Procedure amendment]

[Submission date] May 28, 1993

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

In the coefficient updating means 8, the FIR filter coefficient (Ck (n); k: number of stages) of the adaptive filter 7 is obtained from the following equation by the least square method. Ck (n) = Ck (n-1) + (Sm (n) .alpha.) / Te (n + k-1) (1) where α is the convergence coefficient and Sm (n) is the microphone 5-
The combined signal of 1, 5-2 and 5-3, Te (n + k-1) is the first
Is a normalized signal from the transfer characteristic simulating means 9, and n is an ordinal number of the digital signal.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

A series of operations of the above noise control device will be described. The average transfer characteristic Hd from the output of the adaptive filter 7 to the microphone 5 and the average transfer characteristic Hm from the microphones 5-1, 5-2 and 5-3 to the filter coefficient updating means 8 are set from the tail pipe 2 as a noise source. Let Hnoise be the average transfer characteristic up to the microphones 5-1, 5-2 and 5-3. The average transfer characteristics Hd, Hm,
Hnoise is for each microphone 5-1, 5-2 and 5-
The transfer characteristics Hd, Hm, and Hnoise of No. 3 may be obtained by weighting the contribution of silencing the noises of the microphones 5-1, 5-2, and 5-3. Further, the noise signal from the tail pipe 2 is Sn, the output signals from the microphones 5-1, 5-2 and 5-3 are Sm1, Sm2 and Sm3, the compensation signal from the adaptive filter 7 is Sc, and the microphone 5 Let the input signal Sm of the coefficient updating means 8 which is the combined output from -1, 5-2 and 5-3 and the difference signal that is the output of the difference signal calculating means 11 be Se . Here, the difference signal Se will be
Used as a noise reproduction signal. Further, the transfer characteristic Hd1 simulated by the first transfer characteristic simulating means 9 and the second transfer characteristic simulating means 10 becomes Hd1 = Hd.Hm (2), and the microphones 5-1, 5-2 and 5-3. The signal Sm0 detected at is as follows.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

The input signal Sm of the coefficient updating means 8 is Sm = Hm.Sm0 (5), and the other input signal Te is the noise reproduction signal Se.
Then, the transfer characteristic Hd1 is calculated by the first transfer characteristic simulating means 9.
It is calculated in consideration. In adaptive filter 7, coefficient updating
Since the filter coefficient is changed by the means 8 so that this input signal Sm becomes zero, the compensation signal Sc which is the output signal of the adaptive filter 7 has Sm = 0, that is, Sm0 = 0.
Is determined from the above equation (2) as follows.

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Babasaki 1-228 Goshodori, Hyogo-ku, Kobe, Hyogo Prefecture Inside Fujitsu Ten Limited

Claims (1)

[Claims] 1. A muffler (1) for extinguishing the noise of automobile exhaust
A noise control device which is arranged near the exit of the tail pipe (2) that emits noise at the end pipe of the tail pipe and eliminates noise from the tail pipe (2). The actuator (20) that outputs the erasing sound, and is installed at least at a position near the actuator (20), at a position apart from the actuator (20) by a certain distance, and at a position on the back side of the actuator 20 where leaked noise exists. Microphone (5-1, 5-2, 5-
3) and a synthesis circuit (6-1) for synthesizing the outputs of the microphones (5-1, 5-2, 5-3) based on their mute contributions.
0) and a noise control device.