Study of the influence of noise pre-processing on the performance of a low bit rate parametric speech coder

This paper describes a prospective study of the contribution of a single-sensor noise pre-processing method, prior to coding, to the performance of a parametric low bit rate speech coder in adverse conditions. The 2.4kbits/s vocoder we use estimates four parameters: fundamental frequency, voicing, linear prediction coefficients and energy. Firstly, we study the influence of different noise levels on the estimated parameters with and without noise reduction system. Secondly, we measure the contribution of (i) each speech coder parameter and (ii) the speech enhancement system to the global output intelligibility. Finally, results show the interest of such a speech enhancement system for low bit rate parameter estimation and underline the interest to adapt different pre-processing techniques for each parameter estimation.