Fricatives: Sound sources and modification
Deborah M. Rekart, Cathy Andrews · The Journal of the Acoustical Society of America · 1992
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 [∫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,’’ [z̢] is similarly analyzed. Wideband and cross-sectional spectrograms are made of [s:∫:] 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.