Perceptual significance of locus equations

Identification curves were estimated for the English consonants /b, d, g/ using five-formant CV synthetic stimuli comprehensively sampling the F2 onset×F2 vowel acoustic space in the vicinity of Sussman’s /b, d, g/ locus equations [H. Sussman etal., J. Acoust. Soc. Am. 90, 1309–1325 (1991)]. The stimuli included ten English monophthongal vowel contexts, eleven levels of F2 onset per vowel, and three levels of F3 onset orthogonally varied with the F2 variable (ten vowels×eleven F2 onsets×three F3 onsets=330 stimuli). After brief training, each subject was presented several repetitions of each of the above 330 stimuli, two repetitions per day, over a period of several days. Subjects were instructed to choose one of five identifications: Initial consonant /b/, /d/, /g/, or /w/ or ‘‘no consonant.’’ Systems of identification curves were visualized as surfaces floating over Sussman’s locus equation space in order to judge the degree of correspondence between his acoustic results and these perception results. The current perception results are also compared to those of a similar experiment utilizing two-formant syntheses [A. Liberman etal., Psychol. Monogr. 68, 1–13 (1954)].