Reduction of Long-time Reverberation by a Center-Clipping Process
O. M. M. Mitchell, David A. Berkley · The Journal of the Acoustical Society of America · 1970
A center clipping process has been found to be effective in removing the reverberant tails of speech produced in a room with long reverberation time without significantly reducing intelligibility. The instantaneous output of a center clipper is zero unless the absolute value of the input exceeds a threshold value and otherwise varies linearly with the input. The input speech is divided into several channels by a set of contiguous band filters each less than 1 oct wide, and the output of each filter is independently center clipped. Harmonic distortions introduced by the center clippers are then removed by an output filter bank identical to the input set of filters. A six-channel system using 23-oct filters (250–3500 Hz) was simulated on a CDC 3300-EA1 8800 hybrid computer to process input speech recorded in an auditorium. Clipping levels were set so that the output of each center clipper was zero approximately 50% of the time. An output tape showing reduction of reverberation will be played.