Role of F0 and amplitude in the perception of intervocalic glottal stops

Glottal stops that occur in vowel-consonant-vowel context are often not realized as stops at all, but rather show voicing that is continuous throughout the glottal constriction gesture. Glottal articulations that are realized in this way are apparently marked by reductions in amplitude and fundamental frequency. In the present study measurements from naturally produced utterances containing the sequence /o?o/ (i.e., a glottal stop separating two identical vowels) were used to create a set of synthetic stimuli that varied in their F0 and amplitude contours. The utterances were resynthesized in six ways: (a) original pitch/original amplitude, (b) original pitch/flat amplitude, (c) flat pitch/original amplitude, (d) flat pitch/flat amplitude, (e) flat pitch/inverted amplitude, and (f) inverted pitch/flat amplitude. Results indicated that: (a) a dip in the pitch contour is nearly always sufficient to cue the presence of a glottal stop in the absence of any drop in amplitude, (b) a dip in the amplitude contour is usually sufficient to cue the presence of a glottal stop, and (c) signals with inverted contours were not heard as glottal stops, indicating that it is not merely an abrupt change that is needed to signal a glottal stop.