The Effect of Clear Speech on Temporal Metrics of Rhythm in Spanish-Accented Speakers of English

This paper presents a comparative analysis of temporal rhythm in native American English talkers and Spanish-accented English talkers producing clear (hyperarticulated) speech and typical, conversational-style speech. Five acoustic measures of comparative vocalic and consonantal interval duration (“temporal metrics”) were obtained from speech samples of 40 adult men and women (half native and half Spanish-accented talkers). In conversational-style speech, vocalic-based metrics differed significantly between native and Spanish-accented talkers, consistent with phonotactic differences between the two native languages. In clear speech, however, all metric values from the Spanish-accented talkers became more English-like and no longer differed significantly from those observed in the native English talkers. Post-hoc analysis revealed that native English talkers increased the duration of both weak and strong vowels in clear speech, whereas the Spanish-accented talkers increased the duration of strong vowels without changing the duration of weak vowels. Listener ease of understanding, as perceived by monolingual English speakers, was significantly improved in clear- compared with conversational-style speech for all talkers. The acoustic data help to explain the changes that result from use of clear speech in nonnative speakers. Together with the improved listener ease of understanding, these data strongly support the further exploration of clear speech as a clinical tool to improve prosody and hence, interpersonal communication, in nonnative speakers.