Variability in fricative production and spectra: implications for the hyper- and hypo- and quantal theories of speech production.

Fricative spectral data are compared with articulatory data from electropalatographic (EPG) recordings in an investigation of coarticulatory effects on the acoustic signal. Data were taken from CV tokens produced by four female speakers of Australian English. Results are presented for the coronal fricatives /theta s [symbol: see text] z [symbol: see text]/ in seven monophthong vowel contexts. The analysis consists of a comparison of spectral centre of gravity (COG) with EPG centre of gravity measured along the horizontal dimension. The correlation between the articulatory and the acoustic data is quite high. Overall, the sibilant fricatives show very little variability in production, while the nonsibilant dental shows a good deal of variability. This is reflected in the spectral output. It is also shown that the alveolar sibilants show more effect from vowel context than do the postalveolar sibilants. These results are interpreted as showing that coarticulatory resistance is indeed greater for sibilant fricatives, but that degree of tongue body raising inherent in the fricative's production must also be taken into account. The results for overall variability are discussed with reference to the Hyper- and Hypo- and Quantal Theories of speech production. It is suggested that sibilant fricatives do not lend themselves to the articulatory imprecision which, according to these theories, characterizes perceptually salient, and typologically common, speech sounds.