US 4,965,832 AGranted

Active noise control

AssigneeGeneral Electric Company

InventorsJohn W. Edwards, Nicolaas M. J. Dekker

Life of this patent

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Abstract

An active noise control system for controlling noise propagated through a duct comprises a first microphone located to receive the propagated noise at a point in a plane perpendicular to the length of the duct. A loudspeaker is located substantially at that plane for introducing sound into the duct. An analog first control circuit is operative in response to the noise received by the first microphone to feed a signal to the loudspeaker such that the sound introduced thereby destructively interferes with the noise at that point. A second microphone is located further downstream to receive residual noise propagated along the duct despite the destructive interference. A second control circuit, responsive to the residual noise received by the second microphone, controls parameters of the analog first control circuit so as to minimize the residual noise. In particular, the first control circuit includes an integrator which has a transfer function which is electrically controlled by the second control circuit.

Claims10

Dependent claims

An active noise control system, comprising:

(a) a duct through which noise to be controlled can propagate from a noise source;
(b) first receiving transducer means located to receive the propagated noise at a point in a plane perpendicular to the length of the duct;
(c) transmitting transducer means located substantially at said plane for introducing sound into the duct;
(d) analog first control means connected in a feedback loop with said first receiving transducer means and said transmitting transducer means and operative, in response to the noise received by said first receiving transducer means, for feeding a signal to the transmittng transducer means such that the sound introduced thereby destructively interferes with the noise at said point, said first control means including integrating circuit means having an electrically-controllable transfer function;
(e) second receiving transducer means located further from the noise source than said plane to receive residual noise propagated along the duct despite said destructive interference;
and
(f) second control means, responsive to the residual noise received by said second receiving transducer means, for controlling parameters of said first analog control means so a to minimize said residual noise.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/342,315Filed 25 Apr 1989
Priority: GB 8810236.329 Apr 1988
Granted: 23 Oct 1990
Term ends: Not estimatedThe source records don’t support an estimate.

Classification13 codes

G10K 11/178
Using interference effects; Masking sound: by electro-acoustically regenerating the original acoustic waves in anti-phase
G10K 11/17853
Methods, e.g. algorithms; Devices: of the filter
G10K 11/17819
Characterised by the analysis of the acoustic paths, e.g. estimating, calibrating or testing of transfer functions or cross-terms: between the…
G10K 11/17857
Methods, e.g. algorithms; Devices: geometric disposition, e.g. placement of microphones