Epoch-based analysis of speech signals

Speech analysis is traditionally performed using short-time analysis to extract features in time and frequency domains. The window size for the analysis is fixed somewhat arbitrarily, mainly to account for the time varying vocal tract system during production. However, speech in its primary mode of excitation is produced due to impulse-like excitation in each glottal cycle. Anchoring the speech analysis around the glottal closure instants (epochs) yields significant benefits for speech analysis. Epoch-based analysis of speech helps not only to segment the speech signals based on speech production characteristics, but also helps in accurate analysis of speech. It enables extraction of important acoustic-phonetic features such as glottal vibrations, formants, instantaneous fundamental frequency, etc. Epoch sequence is useful to manipulate prosody in speech synthesis applications. Accurate estimation of epochs helps in characterizing voice quality features. Epoch extraction also helps in speech enhancement and multispeaker separation. In this tutorial article, the importance of epochs for speech analysis is discussed, and methods to extract the epoch information are reviewed. Applications of epoch extraction for some speech applications are demonstrated.