Research On Morphological Approaches To Speech Signal Processing

The digital speech processing, as the very core technology of the information field, is a broad intercrossing subject. Furthermore, it is indicated that the speech signal is actually a complicated non-linear non-stationary processes. Recent research effort has started to migrate to analyze speech signal using non-linear theory. These newly developing non-linear theories make up for the imperfections of the traditional linear techniques.Digital morphological filter is one of the most important and rapidly developing non-linear filter. It has found wide applications in many research fields, such as image analysis and processing, biomedical signal processing, etc. It is a possibility that mathematical morphology will be a new perfect application to the non-linear speech signal processing. In this paper, two morphological approaches to speech processing are proposed. One is a new morphological speech enhancement technique which is to construct a serial morphological filter with the positive and negative parabola structuring elements in different size in order to suppressing white Gaussian and pulse noise embedded in a speech signal. The other is to design a morphological filter with disk structuring elements in different size applying to pitch contrail smoothing. Both methods here are compared with classical approaches. Simulations results confirm the feasibility of these two new approaches. Moreover, it is shown that this morphological speech enhancement algorithm is the same as or superior to the conventional methods, even for the purpose of removing the pulse noise, and the morphological smoothing filter can get the preferable accurate pitch contrail of mandarin. Because of the briefness in algorithm, the directness in results, and the quickness in calculating, mathematical morphology will be a preferable approach to non-linear speech signal processing.