An Enhanced LPC Vocoder with No Voiced/Unvoiced Switch

Abstract

A modified LPC system (LPC plus) which requires no voiced/unvoiced switch at the synthesizer is presented in this paper. The excitation functions of the synthesizer filter are modeled to be the sum of the conventional pulse and noise sources. The mixture ratio is estimated from the LPC residual error signal, and this parameter controls the amplitudes of the pulse and noise sources. Since the V/UV switch is eliminated, this system produces robust speech in highly noisy environments, while a conventional LPC system produces degraded speech due to voicing errors. In addition, this technique has been applied to the speech of two simultaneous speakers and produces synthesized speech which is more natural and intelligible than that produced by conventional LPC. Copyright © 1984 by The Institute of Electrical and Electronics Engineers, Inc.