Enhancing Acoustic Voice Quality Through Real-Time Auditory Feedback Modulation

Auditory feedback modulation (AFM)-altering how speakers hear their own voice during phonation-is a well-established method for investigating vocal motor control. Healthy speakers typically respond to AFM with compensatory vocal adjustments in the opposite direction of the perturbation, such as lowering pitch in response to upward pitch shifts. However, whether degradations in voice quality within auditory feedback elicit comparable compensatory behavior-specifically, vocal adjustments that enhance acoustic voice quality-remains unknown. To address this gap, the present study pursued two aims: (1) to introduce and evaluate a real-time voice resynthesis system, VQ-Synth, designed to induce the percept of hoarseness in otherwise healthy voices, and (2) to test whether hoarseness-induced auditory feedback leads to compensatory improvements in acoustic voice quality, measured by smoothed cepstral peak prominence (CPPS). In Study 1, participants rated recordings of their own voice processed with four different resynthesis methods. Overall, the anti-peak-window method, which inserted noise between the pitch-related amplitude peaks, produced the strongest percept of dysphonia. In Study 2, this method was applied in an AFM experiment to modulate voice quality in real time. Participants sustained the vowel // 140 times. In the AFM group, auditory feedback was modulated according to a phase design (baseline, ramp, hold, and after), whereas the control group received unaltered feedback throughout. CPPS in the AFM group increased significantly from baseline through ramp and hold and remained elevated in the after phase, while there was no CPPS increase in the control group. These results indicate that the observed improvement in acoustic voice quality cannot be attributed to practice effects, but was specifically driven by hoarseness-induced AFM. Future work will explore VQ-Synth's potential in connected speech and its application as a therapeutic tool for individuals with dysphonia.