In this paper

the research focuses on pitch detection techniques of the low-rate WI speech coding.As the pitch doubling and halving problems of pitch detection often occurred with varied noises and Signal to Noise Ratio (SNR)

voice activity detection (VAD) algorithm based on DCT band-partitioning spectral entropy is employed in pre-processing to separate speech and non-speech segments.In order to provide an accurate-pitch-cycle speech for pith detection algorithm

an improved speech decomposition algorithm in DCT domain based on the Harmonic-Noise Model is presented.Then

using the same characteristic of maximum peaks of MCAMDF and NCCF and two pro-processing techniques mentioned above

a pitch detection algorithm in a combination both of two functions together named MCAMDF-NCCF is proposed.In order to satisfy the needs of the pitch accuracy of WI coder and synthesize phase track correctly

a super resolution pitch detection algorithm named MCAMDF-NCCF-FRAC based on MCAMDF-NCCF is also given to get fractional pitch.We applied these algorithms to WI coder

the results from the subjective A/B listening test indicated that both of these two algorithms have a great performance and heavily reduce pitch doubling and halving and voiced-unvoiced error in low SNR

the quality of the synthesized speech satisfies the accuracy of the pitch detection techniques of WI coder completely.