Method and device for active noise reduction in a local area
US5559893A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 21, 1995 |
| Grant date | Sep 24, 1996 |
| Priority date | — |
| Expiry date | Mar 21, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG10K2210/3221
- WIPO fieldOther consumer goods
- WIPO sectorOther fields
Abstract
A method for active noise reduction based on destructive interference of sound waves in order to reduce the energy in a sound field employs two omnidirectional microphones (M1, M2) provided in connection with a loudspeaker. The acoustic feedback of the microphones is eliminated by a closed loop consisting of the microphones and the loudspeaker. The loudspeaker used is an open loudspeaker with a dipole characteristic, thus causing one of the microphones to be more sensitive to the far field and thereby to the noise which has to be suppressed. The method is implemented by a device which comprises a digital signal processor (DSP) for processing the microphone signals and which transmits an output signal to the loudspeaker where the feedback component from the loudspeaker is substantially eliminated, while the output signal's phase and amplitude are adjusted in such a manner that an effective cancellation of the noise is obtained in an area around the loudspeaker's near field. The DSP can preferably be implemented in the form of software modules on an integrated circuit. With the method and the device an integrated reduction in noise level of almost 20 dB is achieved depending on how t…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.