For GA /h/, some friction is created in the glottis, as a result of a slight constriction of the vocal cords. However, additional friction is usually produced by the flow of air through the entire vocal tract, i.e. through the pharyngeal and oral cavity. Since the shape of the vocal tract for /h/ will vary with the quality of the following vowel, the quality of the cavity friction that is produced will vary accordingly. From a purely phon