Cepstrum Pitch Determination

The cepstrum, defined as the power spectrum of the logarithm of the power spectrum, has a strong peak corresponding to the pitch period of the voiced-speech segment being analyzed. Cepstra were calculated on a digital computer and were automatically plotted on microfilm. Algorithms were developed heuristically for picking those peaks corresponding to voiced-speech segments and the vocal pitch periods. This information was then used to derive the excitation for a computer-simulated channel vocoder. The pitch quality of the vocoded speech was judged by experienced listeners in informal comparison tests to be indistinguishable from the original speech.