Phonetic and phonological effects in production and perception of Croatian clear speech

Abstract

This paper examines the interaction of language-general, signal enhancement strategies and language-specific, phonological enhancement strategies in clear speech production and perception in Croatian, a language with a phonemic vowel length contrast and a relatively small inventory of five vowel qualities. Two native speakers of Croatian (one male, one female) read 20 nonsense sentences in conversational and clear speech. In a sentence-in-noise perception test, native Croatian listeners more accurately recognized words produced in clear than in conversational speech by both talkers. However, this clear speech intelligibility benefit was greater for the male than the female talker. Acoustic analyses showed that in clear speech both talkers enhanced the overall acoustic salience of the signal (slower, more frequent pauses, wider pitch range) and expanded the vowel space, although the male showed slightly less extensive vowel space expansion. However, only the male talker enhanced the phonemic vowel length contrast, suggesting that the observed asymmetry in the clear speech intelligibility benefit between the talkers may be due to the contribution of this phonological enhancement feature of his (but not her) clear speech production. The results suggest that speech intelligibility is most effectively enhanced by acoustic-phonetic modifications that reflect a combination of acoustic-auditory and phonological factors.