Electrical audio signal processing systems and devices – Circuitry combined with specific type microphone or loudspeaker
Reexamination Certificate
1998-10-23
2002-07-30
Isen, Forester W. (Department: 2644)
Electrical audio signal processing systems and devices
Circuitry combined with specific type microphone or loudspeaker
C381S369000, C359S199200, C359S199200
Reexamination Certificate
active
06427014
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Ivention
This invention relates to microphones.
2. Description of the Prior Art
Known microphones convert an analogue sound waveform (i.e. physical variations in air pressure) into an analogue electrical audio signal. If a digital audio signal is required, the analogue signal has to be converted by a digital to analogue converter (DAC) into the digital audio signal.
This extra stage of analogue to digital conversion requires extra components and, more importantly, is not a lossless process. In other words, some of the information contained in the original analogue audio signal is lost by the conversion process, through conversion errors or noise.
It would be desirable to provide a microphone which generates a digital audio signal directly from the air pressure variations representing the actual sound.
SUMMARY OF THE INVENTION
This invention provides a microphone comprising:
a diaphragm movable in response to incident sound waves;
a position sensor for generating an electrical position signal indicative of the position of the diaphragm;
a thresholder for generating a one-bit digital signal indicating whether the position signal is above or below a threshold signal level;
a delay for delaying the digital signal; and
a diaphragm driver for moving the diaphragm in response to the digital signal and in an opposite sense to the motion of the diaphragm represented by the digital signal.
REFERENCES:
patent: 4395593 (1983-07-01), Flanagan
patent: 5051799 (1991-09-01), Paul et al.
patent: 5548658 (1996-08-01), Ring et al.
patent: 5621806 (1997-04-01), Page et al.
Frommer William S.
Frommer & Lawrence & Haug LLP
Gordon Kessler
Isen Forester W.
McChesney Elizabeth
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