On a new vocoder technique by the nonuniform sampling

To reduce the redundancy within samples that result from a uniform sampling method like PCM, nonuniform sampling or nonredundant-sample coding methods can be considered. However, it is well known that when conventional nonuniform sampling methods are applied directly to the speech signal, the required amount of data is comparable to, or more than that of the uniform sampling method. To overcome this problem, a new nonuniform sampling method is proposed, in which nonuniform sampling is applied to the low-pass filtered speech signal and the remaining signals are compensated by 16 colored Gaussian random noise with various noise levels. By this method, the speech signal waveform can be encoded by a 1.8 times larger compression ratio than that of the conventional nonuniform sampling method.