Noise reduction circuitry for audio signals

In a circuit of the type for processing signals in the form of a carrier modulated by an audio signal, said modulated carrier signal being subject to defects therein, said circuit including a demodulator for recovering the modulation signal from said carrier, said circuit further including defect compensation circuitry comprising:

• a defect detector responsive to the modulated carrier signal for producing control signals upon the occurrence of signal defects;
• delay means responsive to the modulated carrier signal for delaying the modulated carrier signal by a time substantially equivalent to an integral number of carrier signal cycles;
• and
• switch means serially connected in the demodulator circuit and responsive to said control signals for applying one of undelayed modulated carrier signal and delayed modulated carrier signal from the delay means to said demodulator in the absence of said control signals and applying the other of said undelayed modulated carrier and the delayed modulated carrier signals from said delay means during the presence of said control signals.

A receiver for reproducing audio signals comprising:

• a tuner for downconverting FM broadcast signals to an IF signal;
• a defect detector responsive to defects in the IF signal for generating control signals;
• delay means responsive to the IF signal for delaying said IF signal by a time substantially equivalent to an integral number of IF carrier cycles;
• an IF narrow band filter having an output terminal coupled to sound reproduction apparatus;
• and
• switch means responsive to said control signal for applying the delayed IF signal from the delay means to said IF filter and for applying the undelayed IF signal to said IF filter otherwise.

Defect compensation circuitry for serial inclusion in a system for processing audio signal in the form of a modulated carrier, said circuitry comprising:

• a first terminal for applying said audio signal thereto;
• control circuitry including a defect detector responsive to said audio signal, for producing control signals upon the occurrence of signal defects;
• delay means having input and output terminals, said delay means providing a signal time delay substantially equivalent to an integral number of cycles of said carrier;
• switch means for applying audio signal from the output terminal of the delay means to the input terminal of said delay means in response to said control signals and for applying audio signal from said first terminal to the input terminal of the delay means otherwise;
• and means for coupling the output terminal of the delay means to an output of said defect compensation circuitry.

A video disc player of the type for receiving a composite signal including at least one relatively low frequency carrier modulated by an audio signal and a relatively high frequency video carrier, including a signal pickup device cooperating with pickup circuitry to produce an electrical manifestation of said composite signal and including further circuitry comprising:

• a first band pass filter responsive to said composite signal for passing said at least one modulated low frequency carrier substantially to the exclusion of the video carrier, said band pass filter being sufficiently broad band to pass impulse noise attendant the recovered signal without being excited into ringing;
• a defect detector responsive to the at least one modulated low frequency carrier for generating control signals upon detecting defects in said at least one low frequency carrier signal;
• delay means having input and output terminals respectively, said delay means delaying at least one modulated low frequency carrier signal by a time substantially equivalent to an integral number of cycles of said low frequency audio carrier;
• switch means responsive to said control signals for connecting the delay means input terminal to the delay means output terminal and for connecting the delay means input terminal for receiving signal from said first band pass filter otherwise;
• and
• a second relatively narrow band, bandpass filter tuned to said at least one low frequency carrier frequency having an input terminal connected to the delay means output terminal and having an output terminal at which a defect corrected low frequency modulated carrier is available.