The Effects of Varying Glide Durations On Diphthong Identification

Traditionally, diphthongs have been described as consisting of an initial steady-state portion, a glide, and a relatively short final steady-state portion. This study investigated the contribution of glides of variable duration, in the presence of steady-state portions of fixed duration, to diphthong identification. The three American English diphthongs /ai/, /au/ and /??/ were synthesized, employing fixed durations for the steady-state portions and varying the duration of the glide from zero (no glide) to approximately 150 msec. Two-vowel sequences, identical to the steady-state portions of the diphthongs and separated by "gaps" of varying durations, were also synthesized. Four different fundamental-frequency values were employed in the synthesis. The stimuli were presented to subjects, who were asked to identify each item as one of the three diphthongs or one of the three possible two-vowel sequences. The glide durations at which identification of the stimuli changed from diphthong to vowel sequence were different for the three vocalic sequences tested; the identification pattern was also influenced by the fundamental-frequency values.