Method and apparatus for improving effective signal to noise ratios in hearing aids and other communication systems used in noisy environments without loss of spectral information
US5794187A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 16, 1996 |
| Grant date | Aug 11, 1998 |
| Priority date | — |
| Expiry date | Jul 16, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04R25/505
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Improved signal to noise ratio to help speech comprehension in a noisy environment is accomplished by selectively downwardly expanding a speech and noise composite signal when the speech signal is absent, thereby lowering signal components which represent noise. An expansion control signal is extracted from the composite input signal. Operation is based on the assumption that when noise alone is present, the input signal amplitude is less than some reference level and that when speech and noise are present together, the input signal amplitude is greater than the reference level. The response rates of gain changes are quite rapid, and do not introduce distortion or other audibly noticeable artifacts of the processing. The amount of downward expansion of the noise alone is small compared to noise gates to further reduce processing artifacts. The methods of realization include use of, in combination and alone, analog compressors and expanders, analog expanders in combination with voltage clamps and/or automatic level control circuits, two-quadrant multipliers in conjunction with digital control, entirely digital means for obtaining the requisite sensing and gain control, and expandor …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.