Surround sound system

A system for producing a horizonal surround sound signal, comprising

• (a) means (1) for sensing sound in an area and for producing an omnidirectional sound signal (W), a depth sound signal (X), and a horizontal sound signal (Y), said depth and horizontal sound signals being a function of said omnidirectional sound signal;
• (b) means for encoding and modulating said omnidirectional, depth, and horizontal sound signals to produce a monophonic audio signal (.SIGMA.), a first subcarrier modulated by an audio signal equivalent to a stereo difference audio signal (.DELTA.) of a stereophonic broad broadcast, a pilot tone at half the subcarrier frequency, and a second subcarrier in quadrature with said first subcarrier and modulated by a third audio signal (T), the signals .SIGMA., .DELTA., and T being defined in terms of the direction of the sound being reproduced, said encoding means comprising
• (1) mixer and amplifier means (2) for processing said omnidirectional and depth sound signals;
• (2) multiplier means (5) for processing said horizontal sound signal;
• (3) first filter means (3) connected with one output of said mixer and amplifier means to produce said monophonic audio signal .SIGMA.,
• (4) second filter means (6) similar to said first filter means and connected with the output of said multiplier means to produce said difference signal .DELTA. at a phase angle with respect to said signal .SIGMA. which is selected from an in phase relationship for all angular values of elevation and azimuth;
• and
• (5) third filter means (4) connected with another output of said mixer and amplifier means to produce said third audio signal T with a phase shift of 90.degree. with respect to said signals .SIGMA. and .DELTA.;
• (c) multiplexer means (7) for multiplexing said signals .epsilon., .DELTA., and T, whereby a high quality stereo signal is produced for transmission.