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US 5,170,433 AGranted
Active vibration control
AssigneeAdaptive Control Limited
InventorsStephen J. Elliott, Philip A. Nelson, Ian M. Stothers
Life of this patent
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AssigneeAdaptive Control Limited
InventorsStephen J. Elliott, Philip A. Nelson, Ian M. Stothers
Estimating the term…
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.
An active vibration control system for reducing, by the generation of secondary vibrations, the vibration generated in a vibration field by a primary source of vibration, comprising
An active vibration control system for reducing, by the generation of secondary vibrations, the vibration generated in a vibration field by a primary source of vibration, comprising
Dependencies are inferred from the claim text.