ASA 124th Meeting New Orleans 1992 October

4pPPa4. Masking of tones and formant frequencies.

Abeer Alwan

Dept. of Elec. Eng., UCLA, 405 Hilgard Ave., Los Angeles, CA 90024

The purpose of this study was to find out whether results of auditory masking theory, established primarily for pure tones, can be used to predict masking of vowel formant frequencies by broadband noise maskers. For this purpose, three sets of 2AFC experiments were conducted. In each experiment, four frozen white-noise waveforms (with similar statistical properties) were used. The task in the first set of experiments, was tone-in-noise detection in which the tones were located at 1100 and 1800 Hz. In the second set, one-formant synthetic vowels were used in vowel-in-noise detection tasks. The formant was located at 1100 Hz in one experiment, and at 1800 Hz, in another. Finally, listeners were presented with pairs of four-formant synthetic vowels in noise: one pair had identical vowels and the second vowel in the second pair had a missing second formant frequency (F2). Subjects were instructed to choose the interval thought to contain the different pair of vowels. The four-formant synthetic vowel was either /(open aye)/-like (formants at 625, 1100, 2700, and 3250 Hz) or /(eh)/-like (formants at 500, 1800, 2700, and 3500 Hz). It was found that, on the average, the masked thresholds of tones and of formant frequencies were predicted well from the signal-to-noise ratio in a critical band centered around the tone or the formant frequency. [Work supported by NIH and NSF.]