Production and perception of clear speech in Croatian and English

Abstract

This paper presents a cross-language comparison of clear speech, a distinct mode of speech production intended to enhance intelligibility. Specifically, it explores whether language specific phonological properties guide the articulatory modifications of clear speech in Croatian and English, and examines whether clear speech enhances intelligibility in both languages. Five Croatian and five English speakers read 20 nonsense sentences in Croatian and English, respectively, in conversational and clear speaking styles. In a sentence-in-noise perception test, listeners recognized words more accurately in clear than in conversational speech in their native language, establishing that the clear speech intelligibility effect is not English-specific. Acoustic analyses showed that both phonemic (e.g., the vowel length contrast in Croatian) and allophonic (e.g., the tense versus lax vowel duration difference in English) contrasts are enhanced in clear speech. Furthermore, speakers enhance contrasts even when categories seem to be sufficiently distinct and there is little chance of confusability. For example, the vowel space is expanded equally in English (with 11 vowels) and in Croatian (with just five vowel qualities). The results suggest that clear speech production is driven by the phonological properties of the language, but at the same time all segments are hyperarticulated regardless of inventory based considerations.