Multi-directional sound system

Abstract

A multi-directional sound system for use in the manufacture of matrix four channel stereophono discs comprises an encoder including a plurality of phase shifters for shifting the phases of a plurality of directional input signals from discrete sound sources by angles corresponding to the directions of the sound sources and a matrix circuit for producing two channel signals, and a decoder for decoding the two channel signals for reproducing the directional input signals.

What is claimed is: 
     
       1. An encoder system for producing two channel signals suitable for recording on a phono disc from first to fourth directional audio input signals, said encoder system comprising: first to fourth input terminals for receiving said first to fourth audio input signals, respectively;   first and second output terminals from which said two channel signals are derived, respectively;   first to fourth phase shifter means coupled to said first to fourth input terminals, respectively, said first to fourth phase shifter means being operative to introduce relative phase differences of about +22.5°, +67.5°, -22.5° and -67.5° between said first to fourth audio input signals;   means connected in circuit with said first phase shifter means for coupling about 0.92 of said first audio input signal to said first output terminal;   means connected in circuit with said first phase shifter means for coupling about 0.38 of said first audio input signal to said second output terminal;   means connected in circuit with said second phase shifter means for coupling about 0.92 of said second audio input signal to said first output terminal;   means connected in circuit with said second phase shifter means for coupling about -0.38 of said second audio input signal to said second output terminal;   means connected in circuit with said third phase shifter means for coupling about 0.38 of said third audio input signal to said first output terminal;   means connected in circuit with said third phase shifter means for coupling about 0.92 of said third audio input signal to said second output terminal;   means connected in circuit with said fourth phase shifter means for coupling about -0.38 of said fourth audio input signal to said first output terminal; and   means connected in circuit with said fourth phase shifter means for coupling about 0.92 of said fourth audio input signal to said second output terminal.   
     
     
       2. .[.A decoder for producing first to fourth output signals from first and second channel signals each including four audio signals having predetermined relative amplitude ratios and relative phase differences of about +22.5°, +67.5°, -22.5° and -67.5° therebetween, said decoder comprising:.]. .Iadd.A decoder for producing first to fourth output signals from first and second channel signals each including at least first, second, third and fourth audio input signals in preselected amplitude and phase-shifting relationships; the amplitude relationship being such that the amplitude ratios of said first and second audio input signals contained in said first channel signal to said first and second audio input signals respectively contained in said second channel signal are substantially 0.9:0.38, and the amplitude ratios of said third and fourth audio input signals contained in said second channel signal to said third and fourth audio input signals respectively contained in said first channel signal are substantially 0.92:0.38, and the phase-shifting relationship being such that, for said first to fourth audio input signals having the same frequency and phase, in each of said first and second channel signals there is a phase difference of substantially 45° between said first and third audio input signals, in said first channel signal said first and third audio input signals lag from said fourth and second audio input signals respectively by substantially 90°, in said second channel signal said first and third audio input signals lead said fourth and second audio input signals respectively by substantially 90°, and said first and third audio input signals in said first channel signal are substantially in phase with said first and third audio input signals in said second channel signal, respectively, and said second and fourth audio input signals in said first channel signal are substantially 180° out of phase with said second and fourth audio input signals in said second channel signal, respectively, said decoder comprising: .Iaddend. first and second input terminals for receiving said first and second channel signals, respectively;   first to fourth output terminals from which said four output signals are derived, respectively;   first to fourth phase shifter means coupled to said first to fourth output terminals, respectively;   means connected to said first input terminal for coupling about 0.92 of said first channel signal to said first phase shifter means;   means connected to said first input terminal for coupling about 0.92 of said first channel signal to said second phase shifter means;   means connected to said first input terminal for coupling about 0.38 of said first channel signal to said third phase shifter means;   means connected to said first input terminal for coupling about -0.38 of said first channel signal to said fourth phase shifter means;   means connected to said second input terminal for coupling about 0.38 of said second channel signal to said first phase shifter means;   means connected to said second input terminal for coupling about -0.38 of said second channel signal to said second phase shifter means;   means connected to said second input terminal for coupling about 0.92 of said second channel signal to said third phase shifter means; and   means connected to said second input terminal for coupling about 0.92 of said second channel signal to said fourth phase shifter means.   
     
     
       3. A decoder according to claim 2 wherein said first to fourth phase shifter means are operative to introduce between input signals thereto relative phase differences of about -22.5°, -67.5°, +22.5° and +67.5°. 
     
     
       4. A decoder according to claim 2 wherein said first to fourth phase shifter means are operative to introduce between input signals thereto relative phase differences of about 0°, -90°, 0° and 90°. .Iadd. 5. An encoding apparatus for encoding at least first, second, third and fourth audio input signals into first and second channel signals, said first and second channel signals being capable of being decoded, at the reproduction side, into at least first, second, third and fourth audio output signals respectively which in use are coupled to at least first, second, third and fourth loudspeakers arranged around a listener, said encoding apparatus comprising: signal combining network means for producing said first and second channel signals by combining said first, second, third and fourth audio input signals in preselected amplitude and phase relationships,   with said phase relationships such that, for input signals having the same frequency and phase, in each of said first and second channel signals said first audio input signal leads said third audio input signal by substantially 45°, in said first channel signal said first and third audio input signals lag said fourth and second audio input signals respectively by substantially 90°, and in said second channel signal said first and third audio input signals lead said fourth and second audio input signals respectively by substantially 90°, and   with the amplitude ratios of said first and second audio input signals contained in said first channel signal to said first and second audio input signals respectively contained in said second channel signal being substantially 0.92:0.38, and with the amplitude ratios of said third and fourth audio input signals contained in said second channel signal to said third and fourth audio input signals respectively contained in said first channel signal being substantially 0.92:0.38, and   with said first and third audio input signals in said first channel signal substantially in phase with said first and third audio input signals in said second channel signal, respectively, and with said second and fourth audio input signals in said first channel signal substantially 180° out of phase with said second and fourth audio input signals in said second channel signal, respectively. .Iaddend. .Iadd. 6. An encoding method for encoding at least first, second, third and fourth audio input signals into first and second channel signals comprising the steps of varying the amplitudes of the input signals, phase shifting the phases of input signals, and mixing the input signals,   the amplitude relationships being such that said first and second audio input signals contained in said first channel signal are larger in amplitude than those contained in said second channel signal, respectively, and said third and fourth audio input signals contained in said second channel signal are larger in amplitude than those contained in said first channel signal respectively, and   the phase-shifting relationships being such that, where said first to fourth audio input signals are assumed to have the same frequency and phase, in each of said first and second channel signals said first audio input signal leads said third audio input signal by substantially 45°, in said first channel signal said first and third audio input signals lag from said fourth and second audio input signals by substantially 90°, respectively, and in said second channel signal said first and third audio input signals lead said fourth and second audio input signals by substantially 90°, respectively, and   said first and third audio input signals in said first channel signal are substantially in phase with said first and third audio input signals in said second audio channel signals, respectively, and said second and fourth audio input signals in said first channel signal are substantially 180° out of phase with said second and fourth audio input signals in said second channel signal, respectively. .Iaddend..Iadd. 7. An encoding method according to claim 6 wherein the amplitude ratios of said first and second audio input signals contained in said first channel signal respectively to said first and second audio input signals contained in said second channel signal are substantially 0.92:0.38, and the amplitude ratios of said third and fourth audio input signals contained in said second channel signal respectively to said third and fourth audio input signals contained in said first channel signal are substantially 0.92:0.38. .Iaddend.