Active noise-suppressive control method and apparatus

Details Active noise-suppressive control method and apparatus Active noise-suppressive control method and apparatus

1996-09-24

1997-11-25

Oh, Minsun

Electrical audio signal processing systems and devices

Acoustical noise or sound cancellation

Adjacent ear

381 94, A61F 1106, H03B 2900

Patent

active

056920555

ABSTRACT:
A reproduced sound is sent from a speaker as a sound source unit provided in a sound field. An error signal is produced by a microphone on the basis of a difference in sound between the reproduced sound from the speaker and noise coming from the outside of the sound field into the sound field. A digital filter has a fixed transfer function approximated to a transfer function of the sound field, to which a signal for driving the speaker is supplied. Variation of the transfer function of the sound field is detected by the digital filter. A difference signal between the error signal and an output signal from the digital filter is calculated by an adder. The difference signal determined by the adder is inputted into an IMC filter. A signal for compensating the variation of the transfer function of the sound field and variation of the noise is produced by the IMC filter. A variable parameter of the IMC filter is set so that an absolute value of a product of a value of an approximated and set amount of variation, a distance from the sound source unit to the error-detecting unit, and the variable parameter of the IMC filter is less than 1. Thus, the noise coming into the inside of the sound field is canceled by using an output sound of the speaker.

REFERENCES:
patent: 5337366 (1994-08-01), Eguchi
patent: 5481615 (1996-01-01), Eatwell
patent: 5524057 (1996-06-01), Akiho
Reports of the 1995 Autumn Meeting of Acoustical Society of Japan, Sep. 27, 1995.
Active Adaptive Feedback Control of Sound Field, Mitsubishi Heavy Industries, Ltd., 1st International conf. on Motion and Vibration Control, Yokohama, Sep. 1992, pp. 1032-1037.
2-Degree-of Freedom Control Approach to Active Noise Control, Inter-Noise 94, Toyota Central R & D Labs., Toyota Motor Corporation, Aug. 1994, pp. 1255-1228.
Feedfoward and Feedback Methods for Active Control, Proceedings of the Institute of Acoustics; Proc. I.O.A. vol. 16 Part 2, 1994, pp. 255-276.
Design of Feedback Controllers Using a Feedforward Approach, Active 95, Jul. 1995, pp. 863-874.
SISO IMC Design for Stable Systems, Robust Process Control, M. Morari E. Zafiriou Prentice-Hall 1989, pp. 57-84.

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