ASA 124th Meeting New Orleans 1992 October

1pSP9. Fricatives: Sound sources and modification.

Deborah Rekart

Cathy Andrews

Dept. of Speech Commun., Penn State Univ., University Park, PA 16802

Formulas in current texts describing sound sources and their modification for fricatives do not help students with little mathematical background. In lab sessions, waveform-editing software and a digital filter are used by pairs of students to show high- and low-frequency components in the fricative--vowel syllable [(sh)i], input with the low-pass filter set to 6300 Hz. In this ``normal'' condition, the high frequencies of the fricative and the low frequencies of the vowel are visible in the waveform. A low-pass filter setting of 1250 Hz blocks high frequencies and the fricative disappears; the signal sounds ``muffled.'' A high-pass filter setting of 1250 Hz blocks low frequencies and the vowel disappears; the signal sounds ``whispered,'' [(yog)] is similarly analyzed. Wideband and cross-sectional spectrograms are made of [s:(sh):] to examine how place of constriction determines the frequency range of the friction noise. Cut-off frequencies and peaks of greatest intensity are visibly higher in frequency for (:s) with a more anterior constriction. Variations in /s/ production are evident with greatest intensity ranging from approximately 4000 to 14 000 Hz.