Subjective Evaluation of a 4.8 kbit/s Residual-Excited Linear Prediction Coder

A 4.8 kbit/s residual-excited linear prediction coder (RELP) with two subband coded basebands was systematically evaluated in terms of intelligibility and overall quality. Intelligibility degradation due to RELP-coding is found to be 6 percent without transmission errors, an additional 6.4 percent with 1 percent bit errors, and 9.8 percent in 10 dB SNR acoustic background noise. Quality of the RELP coded speech is midway between those of 3 and 4 bit log-PCM and is significantly higher than that of the pitch-excited linear prediction coder.