Pitch Discrimination for Synthetic Vowels

A psychoacoustic experiment to determine the just-discriminable changes in the fundamental frequency of synthetic vowels is described. The experimental variables investigated are: three synthetic vowels (/i, α, æ/), two sound pressure levels (60 and 80 db re 0.0002 dyne/cm2), and two fundamental frequencies (80 and 120 cps). A method of constant stimuli is employed in which subjects judge the pitch of the vowel as “higher” or “lower” in comparison to a fixed standard. The data indicate that the changes in fundamental frequency discriminated correctly 75% of the time are of the order of 0.3 to 0.5 cps. Application of the results to speech compression is suggested.