Electrical audio signal processing systems and devices – Binaural and stereophonic – Quadrasonic
Patent
1988-01-22
1990-01-02
Isen, Forester W.
Electrical audio signal processing systems and devices
Binaural and stereophonic
Quadrasonic
H04S 300
Patent
active
048918393
ABSTRACT:
Decoding apparatus is disclosed providing desirable multichannel separation among various signals received in a channel pair and distinguished by relative phase and amplitude, including re-distribution of output vs. input signal nulls or positions on the "phase-amplitude sphere." Disclosed separation enhancement circuits are characterized by improved economy and signal purity. Enhancement is preferably controlled within the circuit by combination of gain-controlled enhancement signals with fixed matrix signals in summing amplifiers or the like. In some embodiments the enhancement signal for one output channel is modified to produce a different enhancement signal for a different output channel. In such separation enhancement, alternatives to the preferred-embodiment variable-gain element may include such commercial devices as expander or noise-reduction chips. Derivation of control voltages for controlling separation enhancement is characterized by economical sensing of various program characteristics such as phase, amplitude and program level changes, and may for example include log ratio direction-sensing circuits. Control-voltage processing in response to sensed program characteristics provides improved smoothness of operation and freedom from anomalous operation. In one embodiment, circuits providing a choice between "panoramic" or "surround" reproduction and "ambience" reproduction of stereo program are disclosed. In another embodiment, optimal miltidirectional separation-enhanced decoding for cinema or video sound is obtained with the use of a single variable-gain element.
REFERENCES:
patent: 3944735 (1976-03-01), Willocks
patent: 3959590 (1976-05-01), Scheiber
patent: 4236039 (1980-11-01), Cooper
Isen Forester W.
Keegan Robert R.
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