Vowel amplitude variation during sentence production

With the goal of synthesizing natural-sounding speech based on higher-level parameters, sources of vowel amplitude variation were studied for sentences having different prosodic patterns. Previous theoretical and experimental work has shown that sound pressure level (SPL) is proportional to subglottal pressure (P_s) on a log scale during production of sustained vowels. The current work is based on acoustic sound pressure signals and estimated P_s signals recorded during the production of reiterant speech, which is closer to natural speech production and includes prosodic effects. The results show individual, and perhaps gender, differences in the relationship between SPL and P_s, and in the degree of vowel amplitude contrast between full and reduced vowels. However, a general trend among speakers is to use subglottal pressure to control vowel amplitude at sentence level and main prominences, and to use adjustments of glottal configuration to control vowel amplitude variations for reduced and non-nuclear full vowels. These results have implications not only for articulatory speech synthesis, but also for automatic speech recognition systems