{HEAD ~ The system} updates an autocorrelation function of the audio signal from samples in the audio signal, estimates {TAIL ~ an autocorrelation function} of the speech signal from the updated autocorrelation function of the audio signal, and calculates a power spectral density of the speech signal using the estimated autocorrelation function 
{ HEAD ~ The system } updates an autocorrelation function of the audio signal from samples in the audio signal , estimates { TAIL ~ an autocorrelation function } of the speech signal from the updated autocorrelation function of the audio signal , and calculates a power spectral density of the speech signal using the estimated autocorrelation function
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