Effects of frequency-modulated auditory tones on the voice fundamental frequency in humans

The sensitivity of audio-laryngeal reflex pathways to sinusoidal changes in the fundamental frequency of complex auditory tones (AF0) was assessed indirectly in three young adult human subjects. The subjects sustained phonation at constant voice fundamental frequency (VF0) and voice intensity while listening to a sawtooth tone whose AF0 varied over time in a sinusoidal fashion (rates = 5-13 Hz). The subjects phonated at a low voice intensity so that the intensity of the auditory tone (80-85 dB SL) completely masked their voice. Using computer signal averaging and Fourier analysis techniques it was found that the sinusoidally modulated AF0 induced similar modulations in the VF0 signal. The VF0 modulations were extremely small in amplitude and showed large phase shifts relative to the auditory input. These findings are discussed in relation to the role of auditory feedback in phonatory control.