Investigating Vowel Duration as a Perceptual Cue to Voicing in the English of Native Spanish Speakers

Researchers in the cognitive sciences, and in particular those in acoustic phonetics, investigate the acoustic properties in the speech signal that enable listeners to perceive particular speech sounds. Temporal cues have been found to convey information about the linguistic content of an utterance. One acoustic characteristic that is particularly well documented in American English is the difference in vowel duration preceding voiced and voiceless consonants, which has been found to play a role in the perception of the voicing of postvocalic word-final consonants. Research on vowel duration and its role in the perception of the voicing distinction of the following consonant has primarily involved data from native English speakers. The purpose of the present study was to investigate the vowel durations preceding word-final voiced and voiceless stops in the English production of four native Spanish speakers. This study sought to determine if differences in vowel duration are exhibited preceding voiced and voiceless consonants in the English production of the native Spanish speakers, and to determine if the vowel durations affected the perception of the voicing distinction of the postvocalic stop by four native English speakers A significant effect of voicing on the vowel durations in the English production of the native Spanish speakers was found. However, the degree of variation in the vowel lengths with respect to voicing was much less than the degree of difference exhibited in native English, and similar to the variation produced in native Spanish. The average mean difference in length with respect to the voicing of the following consonant was 17.8 msec. in the present study. In native English the mean difference between vowels preceding voiced and voiceless consonants ranges from 79 msec. to 92 msec. and in Spanish the average mean difference is 18 msec. Statistical analysis performed to quantify the contribution of vowel duration on the perception of the voicing distinction found only minimal affect. It was concluded that although the cue of vowel duration variation was present in the speech signal of this data, the listeners generally did not utilize it as a cue to the voicing distinction of the following stops