JP2928967B2 - Noise control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise elimination device for eliminating noise by active noise control in a noise environment.

[0002]

2. Description of the Related Art In recent years, there has been proposed an active noise control method in which a control sound generated by a digital signal processing technique is output from a speaker and environmental noise is silenced at a listening position.

FIG. 3 is a block diagram showing a configuration of a conventional noise canceling device. In the figure, 1 is a noise source, 2 is a noise detector for detecting noise, 3 is a coefficient updater for updating the coefficient of the adaptive filter 5, 6 is a control speaker for converting the output of the adaptive filter 5 to sound, and 7 is noise. This is an error detector provided at a position where the transfer function G has passed from the source 1. C indicates a transfer function from the control speaker 6 to the error detector 7.

The operation of the above configuration will be described.
The noise output from the noise source 1 is detected by the noise detector 2, the detection signal is subjected to digital signal processing by the adaptive filter 5, and output from the control speaker 6. An error detector 7 detects noise at a position passing through the transfer function G from the noise source 1 and a signal passing through the transfer function C from the control speaker 6. The signal detected by the error detector 7 is an error signal remaining after noise is not eliminated. The error signal and the signal detected by the noise detector 2 are input to the coefficient updater 3, and the adaptive filter 5 is output by the output. Is updated so that the error signal of the error detector 7 becomes smaller.

[0005]

In such a conventional noise control apparatus, the correlation between the signal of the noise detector 2 and the noise signal of the error detector 7 is caused by a nonlinear factor or the influence of a plurality of other noise sources. When it is low, there is a problem that the adaptive filter 5 does not converge stably.

The present invention solves the above-mentioned problem. Even when the correlation between the noise signal detected by the noise detector and the noise at the position of the error detector is low, the adaptive filter 5 is stably converged without diverging. It is an object of the present invention to provide a noise control device capable of suppressing noise by using the noise control device.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a noise detector for detecting the sound and vibration of a noise source, and performs signal processing by inputting a detection signal of the noise detector. An adaptive filter, a control speaker that converts the output of the adaptive filter into a control sound and outputs the control sound, and an error detector that detects, as an error signal, a combined sound of the control sound from the control speaker and the noise from the noise source. the coefficient update calculator for calculating the update amount of the coefficient of the adaptive filter to input and output of the noise detector and the output of the error detector, the update
An integrator that integrates an amount and outputs the integrated filter to the adaptive filter, and outputs an output of the integrator to the coefficient of the adaptive filter.
A noise control device for updating the coefficients of the adaptive filter by adding.

[0008]

According to the present invention, in the above configuration, the integrator temporally integrates the signal of the coefficient update arithmetic unit to remove high-frequency components, which are minute fluctuations of the coefficient update signal, and stably converge the adaptive filter.

[0009]

【Example】

(Embodiment 1) Hereinafter, an embodiment of a noise control device of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of this embodiment. In FIG. 1, the same components as those of the conventional example are assigned the same reference numerals, and the detailed description is omitted. This embodiment is different from the conventional example in that an integrator 4 for integrating the output of the coefficient update calculator is provided.

The operation of the above configuration will be described.
An error signal at a position where noise is controlled is detected by an error detector 7, and the error detection signal and an output signal of the noise detector 2 are input to a coefficient update calculator 3, and the LMS (least
A coefficient update operation is performed using a mean square method or the like, and the signal is input to the integrator 4 to perform temporal integration processing. This process is a process for removing high-frequency components in terms of frequency, and updates the coefficient of the adaptive filter 5 based on the output. An integrator that further integrates the output of the coefficient update calculator 3
4 is added to the coefficient of the adaptive filter 5
Since the coefficients of the adaptive filter are updated, high-frequency components, which are small fluctuations of the coefficient update signal, are removed, and the adaptive filter 5 can be made to converge stably.

(Embodiment 2) Hereinafter, a second embodiment of the noise control device of the present invention will be described with reference to the drawings.
FIG. 2 is a block diagram showing the configuration of the present embodiment. In the figure, reference numeral 3 denotes a coefficient update arithmetic unit, 4 denotes an integrator, and 5 denotes an adaptive filter. The integrator 4 has one tap per tap of the adaptive filter 5.
It is characterized by comprising an IIR digital filter comprising a plurality of memories and a multiplying / adding device to suppress an increase in the amount of hardware. Other configurations are the same as those in FIG.

The operation of the above configuration will be described. The noise detector 2 detects noise from the noise source 1 and inputs the noise to the coefficient update calculator 3. The coefficient update calculator 3 is a filtered XL
The calculation is performed by the MS algorithm. ("Adaptive S
ignal Processing. page 288-300 "B.Widrow 198
5 See Prentice-Hall). The signal at time j of the signal detected by the noise detector 2 is defined as xj. Noise detection signal x
j is input to the N-tap memory line as a signal yj through an FIR filter having coefficients of impulse responses c (0) to c (M) of the space transfer function C, and converges on an error signal ej detected by the error detector 7. The signal multiplied by the constant μ is multiplied by each tap output to obtain coefficient update signals △ h (0) j to △ h (N) j.

That is,

[0015]

(Equation 1)

The integrator 4 calculates the output of the integrator one sample before by β
The value is multiplied by (0 <β <1), added to the coefficient update signal, stored in the memory, and newly added to the coefficient update signal as △ h ′ (0) j to △ h ′ (N) j. That is, Δh ′ (i) j = βΔh ′ (i) j−1 + Δh (i) j i = 0,..., N-(3) The adaptive filter 5 converts this integrator output into one sample. The coefficient h of the adaptive filter is calculated by adding the previous coefficient h (0) j-1 to h (N) j-1.
(0) j to h (N) j, perform an FIR filter operation with the noise detection signal xj, and output it to the control speaker 6 as an output signal oj. That is,

[0017]

(Equation 2)

As described above, in this embodiment, the integrator 4 performs exponential averaging over time. On the other hand, in the frequency domain, when equation (3) is expressed by z-transform, the coefficient H ′ (j) at the i-th tap becomes

[0019]

(Equation 3)

## EQU2 ## which represents the low-pass filter characteristics. As described above, the adaptive filter 5 further integrates the update coefficient output from the coefficient update calculator 3 with the update coefficient.
Since the coefficient is updated by adding the output of the integrator 4, fine fluctuations of the coefficient update signal, that is, high-frequency components are removed, and the adaptive filter 5 can stably converge.
Further, according to the present embodiment, the scale of the hardware constituting the integrator can be reduced.

[0021]

As is clear from the above embodiments, according to the present invention, a noise detector for detecting the sound and vibration of a noise source, and a signal processing is performed by inputting a detection signal of the noise detector. An adaptive filter, a control speaker that converts the output of the adaptive filter into a control sound and outputs the control sound, and an error detector that detects, as an error signal, a combined sound of the control sound from the control speaker and the noise from the noise source. A coefficient update calculator that receives the output of the error detector and the output of the noise detector to calculate an update coefficient of the adaptive filter, and integrates an update amount of a coefficient of the adaptive filter by the coefficient update calculator. and a integrator output to the adaptive filter Te, by which is adapted to update by adding the output of the integrator to the coefficients of the adaptive filter, the influence of nonlinear factors and other plurality of noise sources Even if the correlation between the noise detected by the signal and the error detector of the noise source is low, stably converge without diverging adaptive filter, it is possible to mute the noise effectively.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a noise control device of the present invention.

FIG. 2 is a block diagram showing a configuration of a second embodiment of the noise control device of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional noise control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Noise source 2 Noise detector 3 Coefficient update arithmetic unit 4 Integrator 5 Adaptive filter 6 Control speaker 7 Error detector

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Hashimoto 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-6-266373 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) G10K 11/178

Claims (1)

(57) [Claims] 1. A noise detector for detecting a sound or vibration of a noise source, an adaptive filter for inputting a detection signal of the noise detector to perform signal processing, and converting an output of the adaptive filter into a control sound. A control speaker that outputs, an error detector that detects a synthesized sound of a control sound from the control speaker and a noise from the noise source as an error signal, and an output of the error detector and an output of the noise detector. a coefficient update calculator for calculating the update amount of the coefficient of the adaptive filter to input, the update
An integrator that integrates an amount and outputs the integrated filter to the adaptive filter, and outputs an output of the integrator to the coefficient of the adaptive filter.
Noise control device for updating the coefficients of the adaptive filter by adding.