Robust CELP coders for noisy backgrounds and noisy channels

The authors examine the robustness of the code-excited linear predictive (CELP) coder, such as its ability to cope with nonspeech and corrupted speech inputs or to survive errors in the transmission of the coder parameters. They describe how they determined the error sensitivity of each coder parameter and identified the error propagation mechanisms. They find that the coder is robust to many kinds of input signals but is sensitive to channel errors. They show that the effect of bit errors can be reduced significantly with relatively simple measures such as repetition of the coder parameters from the most recent error-free frame. Incorporating these techniques into CELP results in a robust system with an acceptable performance for both burst and random bit errors rates of up to 1%. The clear channel performance degrades slightly (0.2 dB) as a result of these techniques