Electrical audio signal processing systems and devices – Monitoring of sound
Patent
1982-06-22
1984-07-17
Pitts, Harold I.
Electrical audio signal processing systems and devices
Monitoring of sound
381 94, 381107, 455219, H04B 110
Patent
active
044610254
ABSTRACT:
A circuit for suppressing background noise of a continuous nature while enhancing speech signals, or signals having the transient temporal qualities of speech, includes a signal multiplier which, in the preferred embodiment, receives the composite audio signal along with a control signal present only when the speech component of the audio signal is present. The control signal may be derived from an AGC circuit having a slow attack, fast decay characteristic to establish a quiescent output level from the AGC amplifier in the absence of speech. An envelope detector is biased to provide a zero output amplitude in response to the quiescent amplifier output level. Speech components appearing in the amplifier output signal are then envelope-detected and filtered to provide the control signal. Alternatively, the control signal can be derived by envelope-detecting the audio signal, filtering the detected signal to remove its d.c. component representing the continuous noise, and then detecting and filtering again. In still another embodiment, the control signal acts upon a constant amplitude instead of the audio input signal in order to provide a speech-responsive tactile vibration for the deaf.
REFERENCES:
patent: 3102236 (1963-08-01), Eichenberger et al.
patent: 4143325 (1979-03-01), Kahn
patent: 4216430 (1980-08-01), Amazawa et al.
Audiological Engineering Corporation
Dwyer James L.
Pitts Harold I.
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