No abstract

Studies of Portuguese phonetics and phonology indicate that fricatives are central to some interesting features of the language, yet studies of Portuguese fricatives have been few and limited. In this study, Portuguese fricatives were analyzed in ways designed to enhance our description of the language and to increase our understanding of the production of fricatives. Corpora of Portuguese words containing /f, v, s, z, P, W/, nonsense words of the pattern =V 1 FV 2 = that follow Portuguese phonological rules, and sustained fricatives were recorded by four native speakers of European Portuguese (two men, two women). Results of analysis show that more than half of the voiced fricatives devoice; devoicing occurs more often in word-final fricatives. Averaged power spectra were computed for all fricatives and parameterized in order to aid comparisons across speaker and across corpus, and to gain insight into the production mechanisms underlying the language-specific variations. Substantial differences were found between spectra of voiced and unvoiced, same-place fricatives. The parameters spectral slope, frequency of maximum amplitude, and dynamic amplitude, derived from previous studies, behaved as predicted for changes in effort level, voicing, and location within the fricative. Changes in syllable stress, however, did not affect the fricatives in a manner consistent with effort level variation. Some combinations were also useful for separating the fricatives by place or by sibilance. r

Due to its aerodynamic, articulatory, and acoustic complexities, the fricative /s/ is known to require high precision in its control, and to be highly resistant to coarticulation. This study documents in detail how jaw, tongue front, tongue back, lips, and the first spectral moment covary during the production of /s/, to establish how coarticulation affects this segment. Data were obtained from 24 speakers in the Wisconsin x-ray microbeam database producing /s/ in prevocalic and pre-obstruent sequences. Analysis of the data showed that certain aspects of jaw and tongue motion had specific kinematic trajectories, regardless of context, and the first spectral moment trajectory corresponded to these in some aspects. In particular contexts, variability due to jaw motion is compensated for by tongue-tip motion and bracing against the palate, to maintain an invariant articulatory-aerodynamic goal, constriction degree. The change in the first spectral moment, which rises to a peak at the midpoint of the fricative, primarily reflects the motion of the jaw. Implications of the results for theories of speech motor control and acoustic-articulatory relations are discussed.

In a search for spectral parameters that can be used to distinguish and to model fricatives, spectral moments, dynamic amplitude, and slope above maximum amplitude were computed for a fricative corpus including sustained fricatives at dierent eort levels, and fricatives in vowel context. Moments varied signicantly by frequency range used in computation. M3 appeared to vary the least across fricative, contrasting with Forrest et al.'s 1988 study. Dynamic amplitude separated sibilants and non-sibilants, as predicted; slope above the maximum amplitude varied signicantly with eort level.