Vocal register effects on vowel spectral noise and roughness: findings for adult females.

The effects of vocal register (vocal fry, modal, and falsetto) on the relative roughness and spectral noise level (SNL) of isolated test vowels (/u/ and/ae/) were investigated. Each of the three vocal registers; the obtained samples were magnetically recorded. A panel of 11 listeners independently verified by perceptual judgments that each recorded sample was produced in the "desired" vocal register. Also, they independently rated (on a 5-point equal-appearing intervals scale) the roughness of each test production. A median of the 11 roughness ratings (MRR) available was then obtained as an index of the roughness of each vowel sample. Additionally, a narrow-band (3 Hz) acoustic spectrum of each test production was made in which measures of vowel spectral noise were obtained. A mean over 25 noise measures per test production (from 100 to 2600 Hz) served as an index of the spectral noise level (SNL) for each vowel sample. The major finding in the study was that the MRR and the SNL for productions of both test vowels diminished significantly across vocal registers, from fry, to modal, to falsetto.