Vowel duration and consonant voicing: A production study
This dissertation focusses on the so-called “voicing effect,” by which vowels tend to be shorter when followed by voiceless stops and to be longer when followed by voiced stops, as exemplified by the English word pair bat vs bad. While the presence of this effect is cross-linguistically widespread, less is known about the source(s) of this phenomenon and competing accounts have been proposed over the decades. In this work, I draw from acoustic and articulatory data of Italian, Polish, and English and offer an overarching account of which aspects of the production of voiceless vs voiced stops, and vowel/consonant sequences in general, contribute to the emergence of the voicing effect.
The results indicate that the voicing effect is the product of a mechanism of compensation between the duration of the vowel and that of the following stop closure. The acoustic temporal relations of consonants and vowels observed in disyllabic (CV́CV) words of Italian, Polish, and English suggest that the duration of the interval between the release of the two stops is not affected by the voicing of the second stop. The release-to-release interval has similar duration in words with a voiceless C2 and those with a voiced C2. Within this temporally stable interval, the timing of the closure onset (the VC boundary) determines the duration of both the vowel and the stop closure.
Ultrasound tongue imaging and electroglottographic data of Italian and Polish further show that the timing of the closure onset of voiced and voiced stops depends on articulatory factors related to the implementation of voicelessness and voicing. In particular, I argue that a delayed closure onset allows for enough tongue root advancement (known to facilitate voicing during closure) to be implemented during the production of the vowel in anticipation of the stop closure. Furthermore, glottal spreading typical of voiceless stops also can affect the timing of closure by anticipating the achievement of closure. These two factors, among other known factors, contribute to the observed pattern of short voiced closures and long preceding vowel duration, and, vice versa, long voiceless closures and short preceding vowel duration.