Active noise control
US4965832A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 25, 1989 |
| Grant date | Oct 23, 1990 |
| Priority date | — |
| Expiry date | Apr 25, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG10K2210/506
- WIPO fieldOther consumer goods
- WIPO sectorOther fields
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.