Effects of speech noise on vocal fundamental frequency using power spectral analysis.
To investigate the relationship between auditory function and vocal fundamental frequency (F0) using binaural masking with speech noise during sustained vowel vocalization. Eight healthy subjects were instructed to vocalize the sustained vowel /a/ at the intensities of 65 to 75 dBA and 90 to 100 dBA as steadily as possible. The phonations without noise masking were compared with the phonations under masking with 85-dBA speech noise presented to both ears through headphones. The F0s were obtained by using autocorrelation of the voice signals and were converted to cents to form a F0 sequence. The power spectrum of the F0 sequence was then acquired using fast Fourier transformation. A significant increase in the power spectrum in the frequency range of <3 Hz (p < 0.05, paired Student t-test) appeared under noise masking. A negative feedback control of the auditory system on F0 is suggested regarding F0 modulations of <3 Hz. The auditory system helps control a stable F0 during sustained vowel production by decreasing F0 modulation at <3 Hz. Power spectral analysis of F0 may be used to assess the interaction between F0 production and auditory feedback.