Method and means for adaptively filtering near-stationary noise from an information bearing signal
US4185168A · kind A · utility
Inventors
Key dates
| Filing date | Jan 4, 1978 |
| Grant date | Jan 22, 1980 |
| Priority date | — |
| Expiry date | Jan 4, 1998 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04R25/453
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An input signal containing information such as speech or music as well as near-stationary noise is applied in parallel to a noise-analysis circuit and a noise-reduction circuit, each of which comprises a plurality of bandpass filters covering the range of frequencies associated with the information. The absolute value, or a function thereof, of the output of each bandpass filter in the noise-analysis circuit is produced and smoothed. The presence of near-stationary noise in the input signal is determined by examining the nature of the smoothed signal in each band assuming noise has a frequency spectrum which does not vary with time or varies only within a narrow range over a predetermined period of time with respect to the spectral parameters of the information signal. If noise is detected, the noise-analysis circuit identifies spectral parameters of the information and/or noise in each band using the smoothed signal therein. In the preferred embodiment of the invention, the bandpass filters of the noise-reduction circuit have gain elements that are adjusted in accordance with the identified parameters to minimize, under some continuous minimization criterion, the effect of the noi…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.