Acoustic correlates of vowel intelligibility in clear and conversational speech for young normal-hearing and elderly hearing-impaired listeners

Abstract

Previous reports on the relationship between clear speech acoustic changes and the clear speech intelligibility benefit for vowels have used an “extreme groups” design, comparing talkers who produced a large clear speech benefit to talkers who produced little or no clear speech benefit. In Ferguson and Kewley-Port (2007), 12 talkers from the Ferguson Clear Speech Database (Ferguson, 2004) were assigned to groups based on the vowel identification performance of young normal-hearing listeners, while Ferguson (2010) chose 20 talkers based on the performance of elderly hearing-impaired listeners. The present investigation is employing mixed-effects models to examine relationships among acoustic and perceptual data obtained for vowels produced by all 41 talkers of the Ferguson database. Acoustic data for the 1640 vowel tokens (41 talkers X 10 vowels X 2 tokens X two speaking styles) include vowel duration, vowel space, and several different measures of dynamic formant movement. Perceptual data consist of vowel intelligibility in noise as reflected by the performance of young normal-hearing and elderly hearing-impaired listeners. Analyses will explore the relative importance of the various clear speech acoustic changes to the clear speech vowel intelligibility effect as well as the degree to which this relationship varies between the two listener groups.