Method and system for matching the sound output of a loudspeaker to the ambient noise level
US4628526A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 12, 1984 |
| Grant date | Dec 9, 1986 |
| Priority date | — |
| Expiry date | Sep 12, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03G3/32
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A microphone picks up a signal in response to both the acoustic output of the speaker and the ambient noise at the loudspeaker location, for example, in an automobile. The microphone output signal and the signal which is to be provided to the loudspeaker with variable amplification are each subjected to envelope detection. The two envelope curve signals are compared to produce a signal representative of their similarity, the similarity being high when ambient noise is low or absent. The similarity signal is then processed with reference to a reference voltage which varies with the setting of the manual volume control of the amplifier interposed ahead of the loudspeaker. That amplifier has an automatic volume control input to which a control signal generated in response to the envelope similarity signal is applied to raise the amplification and the loudspeaker output level when ambient noise, detected by the similarity of the envelope signals, is present or increases. The system and method have the advantage that special calibration of the system in place of use, for proper balancing of the microphone output against the useful signal is made unnecessary. The envelope signal comparis…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.