A study on improving accuracy of LPC transmission parameter under digital mobile telephone network

Abstract

In speech communication under digital mobile telephone network environment, It needs to process speech signal before it sends. In this process, it is the first consideration to extract the formant information contained in speech signal. The formant refers to the peak of the spectrum signal envelop responding to the vocal tract filter in the frequency domain. To extract the formant, the LPC parameter is calculated and then, is converted to LSP coefficient, in which process the influence of fundamental frequency (the pitch) is great. Particularly, in case of female speech, since the fundamental frequency and the first formant are located in almost same position, LSP resolution is reduced significantly. In this study, a simple method is proposed to improve the accuracy of LSP through the process of compensating the fundamental frequency using the alteration of the pitch, that is, it is the method to extract the LSP coefficient accurately after accentuating the characteristics of the formant by reducing the high fundamental frequency to increase the pitch, the number of harmonics. © 2012 Springer-Verlag.