水声通信中低码速率语音编码算法的研究

中远距离(>10 km)水声语音通信时,由于可利用带宽窄、复杂多变等不利因素对信息传输率的制约,语音编码速率应降到尽可能的低。利用水声信道传播时延大的特点,结合人耳听觉感知的特性,在深入研究混合激励线性预测编码(MELP)标准之后,提出一种语音编码速率可调节的变比特率语音编码算法。其平均码速率约600 bps,主观语音质量评估平均得分(PESQ MOS)约2.8分。对该编码算法性能进行了计算机仿真和海上实验验证。实验及仿真表明,在误码率不高于10-3时,本算法表现良好且稳定,合成语音清晰可懂,易于辨认说话人。 

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

At medium or long distance(>10 km)underwater acoustic speech communication,bit rate is constrained by the complicated,time varying channel and limited bandwidth of communication system.The bit rate of speech coding is required to be as low as possible.The large 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 speakers.