A study of three coders (sub-band, RELP and MPE) for speech with additive white noise

The following three speech coders are implemented for a bitrate of 9.6 kbits/s 1) Sub-band coder, 2) Residual Excited Linear Predictive (RELP) coder, and 3) Multi-Pulse Excited linear predictive (MPE) coder. Performance of these coders is evaluated for speech corrupted by additive white noise. Evaluation of speech coders is done both subjectively and objectively. The MPE coder is found to give the best performance among the three coders. It is also shown that the MPE coder can be used for noisy speech with signal-to-noise ratio as low as -10 dB giving reasonably good quality speech provided 1) one does not use the error weighting filter and 2) one can use a better LP analysis algorithm which can estimate LP coefficients correctly from noisy speech.