Spectral Noise Levels and Roughness Severity Ratings for Normal and Simulated Rough Vowels Produced by Adult Males

Twenty normal-speaking adult males sustained productions of each of the vowels /u/, /i/, /Λ/, /a/, and /æ/ first normally and then with simulated vocal roughness at one intensity. A tape recording of each production was rated for roughness on a five-point equal-appearing-intervals scale by 11 trained judges and was also analyzed to produce its 3-Hz bandwidth frequency-by-amplitude acoustic spectrum. The median roughness rating and the level of inharmonic spectral components, i.e., noise components, for each production were examined and related. Noise levels for the productions of each vowel averaged over selected spectral ranges between 100 Hz and 8000 Hz correlated highly with the median roughness ratings for those productions. Multiple correlation coefficients indicating the relationship between the median roughness rating and multiple measures of spectral noise in the range from 100 Hz to 2600 Hz for the individual productions of each test vowel were high (≥0.97) and significant for all five vowels.