【Title】Study of low bit rate speech codec algorithm in underwater acoustic communication

【Author】XIAO Dong;MO Fuyuan;CHEN Geng;GUO Shengming;MA Li;Key Laboratory of Underwater Acoustic Environment,Chinese Academy of Sciences;University of Chinese Academy of Sciences;Institute of Acoustics,Chinese Academy of Sciences;

【Abstract】At medium or long distance（> 10 km） underwater acoustic speech communication,information transfer rate is constrained by the complicated,time varying channel and limited bandwidth.The bit rate of speech coding is required to be as low as possible.The time delay of underwater acoustic wave propagation can be used for low bit rate speech coding.After investigating the Mixed Excitation Linear Prediction（MELP） standard and taking account of the auditory perceptual features,a variable and adjustable bit rate speech codec algorithm has been proposed,whose average bit rate is about 600 bps.The average Perceptual Evaluation of Speech Quality Mean Opinion Score（PESQ MOS） of synthesized speeches is about 2.8.It has been proved by the computer simulation and sea trial that the performance of the proposed algorithm is well and robust when bit error rate is no more than 10-3.The synthesized speech is vivid and intelligible,and keeps main individual characteristics of speaker.