a device to monitor vocal information such as vocal volume and frequency and provide such information in a plurality of forms , such as tactile , audible , temporal , and visual ; and to induce altered vocal volume and / or frequency by altering how the user hears his or her voice , such as by shifting the frequency at which the user hears his or her own voice ; for the treatment of vocal nodules , parkinson &# 39 ; s disease , or stuttering .