Determining the relevance of different aspects of formant contours to intelligibility

Abstract

Previous studies have shown that “clear” speech, where the speaker intentionally tries to enunciate, has better intelligibility than “conversational” speech, which is produced in regular conversation. However, conversational and clear speech vary along a number of acoustic dimensions and it is unclear what aspects of clear speech lead to better intelligibility. Previously, Kain et al. [J. Acoust. Soc. Am. 124 (4), 2308–2319 (2008)] showed that a combination of short-term spectra and duration was responsible for the improved intelligibility of one speaker. This study investigates subsets of specific features of short-term spectra including temporal aspects. Similar to Kain’s study, hybrid stimuli were synthesized with a combination of features from clear speech and complementary features from conversational speech to determine which acoustic features cause the improved intelligibility of clear speech. Our results indicate that, although steady-state formant values of tense vowels contributed to the intelligibility of clear speech, neither the steady-state portion nor the formant transition was sufficient to yield comparable intelligibility to that of clear speech. In contrast, when the entire formant contour of conversational speech including the phoneme duration was replaced by that of clear speech, intelligibility was comparable to that of clear speech. It indicated that the combination of formant contour and duration information was relevant to the improved intelligibility of clear speech. The study provides a better understanding of the relevance of different aspects of formant contours to the improved intelligibility of clear speech.

Clear Speech Variants: An Acoustic Study in Parkinson's Disease

“…Acoustic variables likely explaining these intelligibility variations are suggested in a variety of studies. For example, segmental metrics such as static and dynamic vowel measures, consonant spectral moments, and consonant distinctiveness measures have been reported as predictors of intelligibility (Amano-Kusumoto, Holsom, Kain, & Aronoff, 2014;Fogerty, 2013;Fogerty & Humes, 2010;Kay, 2012;Kim et al, 2011;Lansford & Liss, 2014;Maniwa, Jongman, & Wade, 2008;Owren & Cardillo, 2006;Tjaden & Wilding, 2004;Turner et al, 1995;Weismer, Martin, Kent, & Kent, 1992). In addition, suprasegmental measures of F0 and global timing measures have shown to be strong predictors of intelligibility (Bradlow, Torretta, & Pisoni, 1996;Bunton, Kent, Kent, & Duffy, 2001;Kim et al, 2011;Laures & Weismer, 1999).…”

Improved tactile speech perception and noise robustness using audio-to-tactile sensory substitution with amplitude envelope expansion

“…It is possible that, when enhancing high-intensity phonemic cues such as formants, envelope expansion impaired perception of less energetic cues, such as low-intensity frication noise for some fricatives or less-intense higher frequency formants for nasal phonemes. Because of the limited frequency resolution and relatively small dynamic range available through vibro-tactile stimulation (~ 55 dB on the wrist 19 ) compared to audio with normal-hearing, high intensity cues that are more important for audio speech perception 31 , such as the first and second formants, were prioritised. Further work is required to establish which speech cues are most effectively perceived through tactile stimulation and whether the cues that are most important when listening to speech are also the most important when feeling speech through tactile stimulation.…”