Investigation of IMBE parameters´ sensitivity to noise

In modern digital communication systems, more and more vocoders are used. At the same time improving their resistance to noise also becomes an important issue since their input speech is often unavoidably corrupted by noise when they work in real world. This paper investigates the improved multi-band excitation (IMBE) parameters´ sensitivity to white noise and the parameter error´s effect on the quality of synthesised speech. As a result a key parameter is found which contributes most to the heavy distortion of the synthesised speech in a noisy environment. Then the possibility of using speech enhancement to reduce such distortion is examined. Finally the results are presented when MMSE-based speech enhancement is applied to the IMBE vocoder