DIFFERENCE LIMENS FOR FORMANT PATTERNS OF VOWEL SOUNDS

Studies of thresholds for discrimination of formant frequency variatio n in synthetic vowel sounds have been predominantly limited to variati ons in a single formant. Here, differences limens (DLs) are presented for multiformant variations expressed in measures of Delta F and as di stances in the auditory-perceptual space (APS) proposed by J. D. Mille r [J. Acoust. Soc. Am. 85, 2114-2134 (1989)]. DLs for four subjects we re estimated along 102 synthetic vowel continua representing five patt erns of formant variation [(1) single variation in F1; (2) single vari ation in F2; (3) parallel simultaneous variation in F1 and F2; (4) opp osing simultaneous variation in F1 and F2; and parallel simultaneous v ariation in F1, F2, and F3] and 17 within-or between-category vowel so unds. Minimal uncertainty methodology was employed utilizing an adapti ve up-down procedure with a cued, two-interval forced-choice (2IFC) ta sk. The results of this experiment reflect smaller DLs for both single - and multiple-formant changes than have been found in the past and al so suggest that discrimination of parallel multiformant variation is s ignificantly better than opposing multiformant or single-formant varia tion.