Electrical audio signal processing systems and devices – One-way audio signal program distribution – Public address system
Patent
1995-05-01
1997-07-15
Isen, Forester W.
Electrical audio signal processing systems and devices
One-way audio signal program distribution
Public address system
381 682, 381 684, 381 93, H04R 2700
Patent
active
056490194
ABSTRACT:
Sound is converted into an electrical signal by a microphone and is converted into an inaudible, pulse width modulated signal that is combined with the electrical signal from the microphone, amplified, and converted into sound waves by a speaker. The pulse width modulator includes an A/D converter coupled to a shift register in a digital encoder. Any sound travelling from the speaker back to the microphone includes the inaudible component representing the original sound. The inaudible component is separated from the audible components, and the original sound is reconstructed in a pulse width demodulator including a shift register in a digital decoder coupled to a D/A converter. The reconstructed original sound is subtracted from the signal from the microphone, thereby reducing any echo and cancelling feedback. The apparatus includes amplitude correction circuitry for flattening the frequency response of the apparatus and includes phase correction circuitry for eliminating phase shifts in the apparatus.
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