Abstract: A sound system is disclosed which, in common with earlier phase-amplitude multichannel "matrix" encode-decode systems, conveys or stores audio programs having multidirectional sound-source localization in a pair of audio-bandwidth channels, whether analog or digital. In the present invention, representation of a vertical, height dimension is added by mapping the "phase-amplitude sphere" representing signal separation onto a spatial hemisphere and by introducing to the parameters of phase difference and amplitude ratio a third parameter, decorrelation. Non-complementary matrices are used for encoding and decoding to provide improved separation between decoded signals. A radius-scaling function facilitates encoding of sound source locations outside, as well as within, the boundaries of the audience space defined by the peripheral and overhead loudspeaker locations.

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.

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.

Abstract: A stereophonic sound system where a plurality of audio signals produced at the program source are encoded to two channels for recording or transmission, and then decoded at playback to produce a plurality of acoustical signals corresponding to those received at the program source. The playback apparatus cooperates with a stereo signal source and includes a plurality of playback channels, the playback channels including gain controlled amplifiers adapted to be coupled to respective loudspeakers. Each of the gain controlled amplifiers is controlled by a control voltage generator that produces a control voltage, the magnitude of which is determined by specified loudness level, phase, and/or waveform characteristics of the signals in the playback channels.