The role of formant amplitude in the perception of /i/ and /u/

Although recent evidence reconfirmed the importance of spectral peak frequencies in vowel identification [Kiefte and Kluender (2005). J. Acoust. Soc. Am. 117, 1395-1404], the role of formant amplitude in perception remains somewhat controversial. Although several studies have demonstrated a relationship between vowel perception and formant amplitude, this effect may be a result of basic auditory phenomena such as decreased local spectral contrast and simultaneous masking. This study examines the roles that local spectral contrast and simultaneous masking play in the relationship between the amplitude of spectral peaks and the perception of vowel stimuli. Both full- and incomplete-spectrum stimuli were used in an attempt to separate the effects of local spectral contrast and simultaneous masking. A second experiment was conducted to measure the detectability of the presence/absence of a formant peak to determine to what extent identification data could be predicted from spectral peak audibility alone. Results from both experiments indicate that, while both masking and spectral contrast likely play important roles in vowel perception, additional factors must be considered in order to account for vowel identification data. Systematic differences between the audibility of spectral peaks and predictions of perceived vowel identity were observed.