EMG evidence for the automaticity of intrinsic F0 of vowels

Abstract

Although vowels can be produced with many F0 values, high vowels’ F0s tend to be higher than low vowels’, a tendency found for every language examined. Nonetheless, this ‘‘intrinsic F0’’ (or IF0) has been called a deliberate ‘‘enhancement’’ of the speech signal, aiding vowel height perception. Since IF0 remains constant with the number of vowels in a language, this enhancement seems unlikely. The only positive evidence for it is that activity of the cricothyroid (CT) muscle, which primarily raises F0, is larger for high vowels than for low. The present experiment explores this by having subjects produce vowels at slightly different F0s, with the differences being similar to the IF0 magnitude for each subject. The first subject (of four planned) showed no vowel height difference in CT; further, an analysis factoring out F0 as a covariate showed that high vowels had higher CT activation. Thus different vowels involve different levels of CT activity for a given F0; previous findings were likely due not to F0 control but to F0/vowel quality interactions. Even the EMG evidence, then, renders IF0 an unlikely speech enhancement. Rather, IF0 appears to be an automatic consequence of vowel production. [Supported by NIH Grant DC-02717.]