A modified CS-ACELP algorithm for variable-rate speech coding robust in noisy environments

This letter deals with a variable bit-rate CS-ACELP speech coder based on new algorithms that are robust in the presence of the background noise typical of wireless communications. The coder presents eight operating modes ranging from 0-8 kbit/s with an average bit-rate of about 4 kbit/s. Subjective and objective comparisons with the recent ITU-T G.729 8 kbit/s standard, used in the discontinuous transmission mode, demonstrate that the proposed coder provides an average bit rate reduction of about 20% maintaining the same algorithmic delay and perceptive quality.