Vocal Pitch and Intensity Effects on Vowel Spectral Noise Level in Condition of Vocal Fatigue

The proliferation of quick methods for analyzing vocal signals has made acoustic voice measurement more practical for clinical application. One measure of interest is the acoustic vowel spectral noise level (SNL). For vowel SNL measurements to be clinically meaningful, however, it is necessary to understand what variables may affect them. For this study, vocal fundamental frequency (f _{rm o}) and phonation intensity effects on vowel /a/^ectral noise level (SNL) for adult females with (N = 10) and without (N = 8) formal singing training were studied. The effects of loud, high-pitched oral reading on SNL were also investigated. Results showed that mean SNL diminished as phonation intensity increased from low to high for both subject groups' phonations at controlled low f_{rm o}. At controlled high f_ {rm o}, however, significant SNL differences across intensities were revealed within the non-singer group only. Here it appeared that the mean SNL diminished as the non-singer group increased phonation intensity, but remained unchanged for the singer-group. For both subject groups' controlled low f _{rm o} phonations, mean SNL increased following 15 minutes of loud, high-pitched oral reading but decreased to pre-reading level following a 1-hour vocal rest period. No SNL differences before -reading, after-reading or after-rest reached significance when subjects phonated at controlled high f_ {rm o}. Results also showed an inverse relationship between f_{rm o} and vowel SNL, although the differences were not statistically tested. The observed trend for decreased SNL to accompany increased vocal f_{rm o}, however, confirms previous findings.