Hearing aid circuit
US4792977A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 12, 1986 |
| Grant date | Dec 20, 1988 |
| Priority date | — |
| Expiry date | Mar 12, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04R25/30
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A hearing aid that is compact and efficient and that provides a high degree of control over its frequency response and also over its output level versus input level characteristic. The frequency response control includes an adjustable four pole high pass filter and an adjustable four pole low pass filter, to define the pass band, and an adjustable slope filter, to define the slope within the pass band. The control over the output level versus input level characteristic includes an input AGC system with well defined, independent control of compression threshold and compression ratio, an adjustable peak clipper, and a selectable output AGC system that tracks the peak clipper setting. The hearing aid incorporates a number of novel circuits including a state variable filter with adjustable corner frequency, a filter that can be continuously adjusted from a single pole low pass characteristic to a single pole high pass characteristic, a circuit to provide a range of reference voltages to accurately set the range of control currents used to control the corner frequencies of the state variable filters, a compansion system surrounding the filter network to effectively increase its limited …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.