  The great majority of current voice technology applications relies on
acoustic features characterizing the vocal tract response, such as the widely
used MFCC of LPC parameters. Nonetheless, the airflow passing through the vocal
folds, and called glottal flow, is expected to exhibit a relevant
complementarity. Unfortunately, glottal analysis from speech recordings
requires specific and more complex processing operations, which explains why it
has been generally avoided. This review gives a general overview of techniques
which have been designed for glottal source processing. Starting from
fundamental analysis tools of pitch tracking, glottal closure instant
detection, glottal flow estimation and modelling, this paper then highlights
how these solutions can be properly integrated within various voice technology
applications.
