Temporal and spectral characteristics of conversational versus read fricatives in American English

The present study compares the production of fricatives in conversational versus read speech in American English. The goal is to examine which parameters contribute to the identification of fricatives across the two speech styles. The study surveys over 162 000 fricative tokens from the Buckeye Corpus [Pitt, Johnson, Hume, Kiesling, and Raymond (2005). Speech Commun. 45, 89-95] and the TIMIT Corpus [Zue and Seneff (1996). Recent Research towards Advanced Man-Machine Interface through Spoken Language (Elsevier, Amsterdam, the Netherlands), pp. 515-525]. A total of 18 different temporal and spectral measures are tested, including segment duration, preceding and following phone duration, spectral moments (at onset, midpoint, and/or offset), spectral peak frequency, etc. Results show that segment duration and midpoint spectral moments make the most prominent contribution to the categorization of fricatives for both speech styles. Spectral measures are more important for conversational speech, whereas duration plays a greater role for read speech. At the same time, the magnitude of the differences across speech styles is often low and many of the observed effects may be attributable to methodological differences across the corpora. Results may indicate that reduction of fricatives in conversational speech is more limited compared to the reduction of other types of speech sounds, such as plosives.