Colouration in assisted reverberation systems

Assisted reverberation systems are used to electronically enhance the reverberation time of an auditorium. A limitation of such systems is that they produce enhanced room transfer functions that contain unnaturally large peaks. These peaks produce colouration of the sound decay. A stochastic simulation technique is presented that quantifies colouration by measuring the probability density function of the transfer functions and comparing it with the ideal Rayleigh distribution of an unassisted room. The technique is applied to existing reverberation systems, and to a new system which provides large increases in reverberation time without increasing the loop gain. It is shown that, for the same power gain, the new system produces a higher colouration, but that this problem may be eliminated by the use of an allpass reverberator