Auditory-Motor Interaction for Vocal Rhythms and Resonance in Individuals With Normal and Pathological Voices

Auditory-motor integration for voice control is essential for precise and flexible vocal outputs. This study aims to investigate the spontaneous adjustments in voice and resonance characteristics when phonation occurs under distinct auditory conditions in individuals with normal and pathological voices.

Voice and nasal surface vibrations, measured by accelerometry, were obtained from 23 individuals with vocal fold nodules (VFN), 10 with muscle tension dysphonia (MTD), and 18 healthy controls during sustained vowel production under three auditory conditions: natural hearing, 90-dBC noise, and 60-dBC noise. Acoustic parameters included vocal fundamental frequency (F0), F0 modulations, jitter, shimmer, relative amplitude perturbation, average perturbation quotient, and intensity. Nasal accelerometric signals were analyzed to examine the effects of auditory and vocal conditions on oral-nasal balance, using both amplitude and power spectral analyses.

Under 90-dBC noise, all groups showed increased vocal intensity. However, only healthy and MTD participants presented significantly increased low-frequency F0 modulations below 3 Hz (LFM), indicative of disrupted auditory feedback. Under 60-dBC noise, LFM changed significantly only in the VFN group, which also exhibited greater mean accelerometric amplitude across auditory conditions. Spectral energy increased in 200-360 Hz for healthy controls under 60-dBC noise, and in 700-1200 Hz for VFN under 90-dBC noise. The MTD group showed no significant changes in nasal vibrations.

This study suggests that auditory feedback influences both F0 rhythms and nasal-oral balance. Individuals with MTD or VFN may exhibit atypical auditory-motor integration, resulting in vocal motor patterns that differ from healthy individuals. Consistent low-intensity auditory stimulation appeared to facilitate vocal modulation, providing preliminary evidence that such input might promote stability and efficiency of vocal function. Further research with larger and more demographically diverse samples is necessary to strengthen the robustness and generalizability of the potential effects.