Target Correlation Approach for Modification of Low Correlated Pitch Cycles of Residual Speech

Pre-assumption for low bit rate speech coding is that pitch evolves smoothly and pitch cycles are highly correlated for voiced speech. Due to non stationary characteristics of speech signal, this assumption is sometimes inaccurate and therefore the performance of speech coder is affected. In this paper, low correlated pitch cycles are specified and then modified using target correlation concept which maintaining perceptual speech quality identical to original speech. Since the modification is performed independently from speech coder, this can be applied as a preprocessing in low bit rate speech coding to provide more regular speech.