With this command you create a new LPC from every selected Sound, using the covariance method.
You are advised not to use this command for formant analysis. For formant analysis, instead use Sound: To Formant (burg)..., which also works via LPC (linear predictive coding). This is because Sound: To Formant (burg)... lets you specify a maximum frequency, whereas the To LPC commands automatically use the Nyquist frequency as their maximum frequency. If you do use one of the To LPC commands for formant analysis, you may therefore want to downsample the sound first. For instance, if you want five formants below 5500 Hz but your Sound has a sampling frequency of 44100 Hz, you have to downsample the sound to 11000 Hz with the Sound: Resample... command. After that, you can use the To LPC commands, with a prediction order of 10 or 11.
The covariance algorithm is decribed in Markel & Gray (1976).
© David Weenink & Paul Boersma, April 7, 2004