Active vibration control

Details Active vibration control Active vibration control

1989-12-11

1992-12-08

Fleming, Michael R.

Electrical audio signal processing systems and devices

One-way audio signal program distribution

Public address system

381 71, 381 94, 395 2, G10L 300

Patent

active

051704331

ABSTRACT:
To reduce noise inside a motor car passenger compartment, two loudspeakers 37.sub.1, 37.sub.2 are driven by signals derived from a reference signal x(n) by adaptive filtering carried out by a programmed microprocessor and memory unit 36 which adapts the filtering in dependence on error signals e.sub.l (n) from four microphones 42.sub.1, 42.sub.2, 42.sub.3 and 42.sub.4 distributed in the passenger compartment. Reference filtering coefficients are initially determined by analysis of finite impulse responses when white noise is acoustically coupled from the loudspeakers 37 to the microphones 42, a white noise generator 48 being coupled to the unit 36. The reference signal x(n) is restricted to one or more selected harmonics or subharmonics of the fundamental noise frequency by a filter 34 which tracks the selected frequency. The selected frequency may be obtained from a coil 31 in the ignition circuit of the vehicle.

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