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wrote: original article:http://www.egroups.com/group/speechcoding/?start% > Hi there, > > can anyone explain to me about the use of pre-emphasize in LPC coding ? > > If we see in the DOD Standard, they use pre-emphasize before the speech is > analyzed with 1 - 0.9375z**1. > I checked using MATLAB that the frequency response of this filter is high > pass, it means that we'll lose the first formant of the speech being > analyzed. If i've not mistaken, the first formant freq. is very important to > characterized the speech, so why they do the pre-emphasize? isnt they gonna > lose the intelegency of the analysis speech? Rabiner and Schafer (1978) page 433 gives a frequency domaininterpretation of the standard LPC mean squared error. To summarise I quote: "it follows that minimising E_n (the mean squared error) is equivalent to minimising the ratio of the energy spectrum of the speech segment to the magnitude squared of the frequency response of the linear system in the model of speech production" The main point being that it is a ratio that is mimimised, so you can play about with the power spectrum and to a first order approximation the LPC model will still fit it. tony robinson speaking only for |