Electrical audio signal processing systems and devices – Circuitry combined with specific type microphone or loudspeaker
Reexamination Certificate
2005-08-09
2005-08-09
Mei, Xu (Department: 2644)
Electrical audio signal processing systems and devices
Circuitry combined with specific type microphone or loudspeaker
C381S174000
Reexamination Certificate
active
06928173
ABSTRACT:
This present invention is related to a capacitor microphone. Capacitance change of a microphone unit without polarization voltage is converted to a digital signal to obtain a sound signal in order that the microphone restricts noise and the productivity of the microphone is increased. The capacitor microphone comprises a first oscillator2which outputs a sound signal varying frequency in response to capacitance change of the microphone unit1, a second oscillator3which outputs a tracking signal varying frequency because of a control voltage CV, a phase comparator4comparing phases of the sound signal and the tracking signal to output lead or lag signal, and an adder-subtracter14outputting digital sound data. An adding-pulse signal and a subtracting-pulse signal, which are obtained by the logical product of the lead-phase or lag-phase signal and clock pulses, are inputted to the adder-subtracter14.
REFERENCES:
patent: 6549631 (2003-04-01), Jackson
patent: 6697493 (2004-02-01), Kern
Kabushiki Kaisha Audio-Technica
Mei Xu
Pendleton Brian T.
Welsh & Katz Ltd.
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