Speech Compression by Polynomial Approximation

Methods for speech compression aim at reducing the transmission bit rate while preserving the quality and intelligibility of speech. These objectives are antipodal in nature since higher compression presupposes preserving less information about the original speech signal. This paper presents a method for compressing speech based on polynomial approximations of the trajectories in time of various speech features (i.e., spectrum, gain, and pitch). The compression method can be integrated into frame-based speech coders, and can also be applied to features that can be represented as temporal series greater in duration than the frame interval. Theoretical issues and experimental results regarding this type of compression are addressed in this paper. Experimental implementation into a 2400 b/s standard speech coder is reported along with objective and subjective evaluations of operation in various noise environments. The new speech coder operates at a transmission rate of 1533 b/s, and for all noisy conditions tested performs better than the 2400 b/s standard speech coder