Abstract
Vibrato enhances the expressiveness of singing, but mastering and controlling it requires advanced vocal skills. If vibrato is controlled through engineering methods, even beginners can achieve high expressiveness. This study develops a system that controls vibrato by applying electrical stimulation to the larynx. This approach enables motor-level control of vocal modulation, linking users’ physical movements to interactions with virtual reality avatars in virtual environments. Experiments were performed to investigate several aspects: whether the extent of vibrato changes depending on stimulation position and it can be controlled by current intensity, whether vibrato rate can be controlled by stimulus frequency, and whether variations in fundamental frequency affect vibrato extent. The results indicate that stimulation position influences vibrato extent. Additionally, vibrato extent significantly differs based on current intensity. The median vibrato rate aligned with the stimulus frequency for eight out of eleven participants, indicating a clear observation of vibrato. A significant correlation was observed between the fundamental frequency of vocalization and vibrato extent for three participants, suggesting that pitch affects vibrato parameters in some cases. These results indicate the feasibility of controlling vibrato rate and extent through adjustment of the stimulation parameters. This system shows the potential for flexible modulation of vibrato extent and rate according to the song, thereby augmenting human singing ability.