Wikipedia
The Variable Room Acoustics System is an acoustic enhancement system for controlling room acoustics electronically. Such systems are increasingly being used to provide variable acoustics for multipurpose venues.
VRAS uses multiple microphones distributed around the room, fed via a multichannel digital reverberator to multiple loudspeakers to provide controllable enhancement of the reverberation time of the room. It is an example of a non-in-line or regenerative sound system which uses the inherent feedback of sound from the loudspeakers to the microphones to enhance the reverberation time for all sound source positions within the room. VRAS uses a unitary reverberator which maintains a constant power gain with frequency so that its inclusion does not affect the stability of the system (at each frequency the reverberator is a unitary matrix).
In addition, VRAS uses a number of microphones close to the stage area to detect early energy from the performers, which is used to generate early reflections. Such systems are termed in-line or non-regenerative. In-line systems aim to minimise the effects of regeneration by detecting stage sound at a high level, and may then be used to generate early reflections or late reverberation.
VRAS is thus a hybrid system that uses both regenerative and non-regenerative approaches.
VRAS was developed by Mark Poletti at Industrial Research Limited, New Zealand and commercialized by LCS Audio. VRAS is now a part of the Meyer Sound Laboratories Constellation System.