Abstract: A modular acoustic sound system for a room for two-way conversations without the need for switching. The system includes pairs of microphones each connected to a phase shifter so that in-phase signals inputted to the microphone pair are shifted 180.degree. apart. The out-of-phase signals are input to a summing circuit having an amplified output which drives a plurality of loudspeakers. A portion of the audible loudspeaker outputs enters the microphone pair, is phase shifted, and cancelled out in the summing amplifier. Any number of loudspeaker/microphone pairs operate in the system and any microphone may be spoken into to drive every loudspeaker.

Abstract: An electronic sound enhancing system for improving the symphonic criteria of sound emanating from a performing shell is provided. Microphones are disposed in the performing shell for receiving sound emanating therefrom and converting same to an audio signal. Reverberant field loudspeakers are positioned with respect to the performing shell to produce low frequency reverberant field sound. Forestage loudspeakers are disposed proximate the shell for emitting sound representative of the early first reflections of the sound emanating from the performing shell. Time delay circuitry disposed intermediate the microphones and the reverberant field loudspeakers and forestage loudspeakers respectively apply the audio signal to the reverberant field loudspeakers delayed by a first predetermined interval of time and to the forestage loudspeakers delayed by a second predetermined interval of time.

Abstract: A sound reinforcement system for a meeting room provides improved effective communication between several individuals located at a distance from one another within a room, as around a large conference table in a corporate boardroom, by positioning a pair of speakers driven out of phase with one another at each individual location and positioning a microphone within the acoustical cancellation zone of the corresponding speaker pair. Acoustical gain is further improved by feeding the signal from each microphone to all speaker pairs except the one to which it corresponds and/or by making the level of a signal arising from a speaker pair proportional to its distance from the microphone that picked up that signal.