Effects of environmental noise on computer-derived voice estimates from female speakers

The purpose of this study was to examine the influence of noise on voice profile statistics from female samples. Six young adult females served as subjects. Five had normal voices; one had a pathological voice with accompanying bilateral vocal nodules. Each female subject was required to match a generated 235 Hz tone (+/- 2 Hz) while maintaining a constant output level of 70 dB SPL (+/- 5 dB). Data collected from a previous study involving a normal male subject were included for comparative purposes. Noise was generated from a personal computer fan which had a strong center frequency component at 235 Hz. Six different A-weighted signal-to-noise [S/N(A)] conditions were created, ranging in 5 dB increments from 25 to 0 dB. Results revealed that fundamental frequency was reasonably resistant to the effects of noise and to the effects of the noisy (pathological) voice signal. Jitter and shimmer estimates generally increased as noise floors elevated. The greatest amount of measurement error was found for the pathological female voice when captured in the presence of environmental noise. Findings are discussed relative to clinical issues surrounding measurement error.