Perception of vowels with missing formant peaks

Although the first two or three formant frequencies are considered essential cues for vowel identification, certain limitations of this approach have been noted. Alternative explanations have suggested listeners rely on other aspects of the gross spectral shape. A study conducted by Ito, Tsuchida, and Yano [(2001). J. Acoust. Soc. Am. 110, 1141-1149] offered strong support for the latter, as attenuation of individual formant peaks left vowel identification largely unaffected. In the present study, these experiments are replicated in two dialects of English. Although the results were similar to those of Ito, Tsuchida, and Yano [(2001). J. Acoust. Soc. Am. 110, 1141-1149], quantitative analyses showed that when a formant is suppressed, participant response entropy increases due to increased listener uncertainty. In a subsequent experiment, using synthesized vowels with changing formant frequencies, suppressing individual formant peaks led to reliable changes in identification of certain vowels but not in others. These findings indicate that listeners can identify vowels with missing formant peaks. However, such formant-peak suppression may lead to decreased certainty in identification of steady-state vowels or even changes in vowel identification in certain dynamically specified vowels.