Objective assessment of the effects of semi-occluded vocal-tract techniques on vocal performance

Semi-Occluded Vocal Tract Exercises (SOVTE), which are based on the increase of the vocal tract impedance through the semi-occlusion of the mouth, are mainly used by speakers and singers, but their use is increasing also in voice therapy. The device VocalFeel®, which is made up of a facemask, a humidifier-filter with a unidirectional valve and a bubble equipment, combines the benefits of SOVTE with the surface hydration of the vocal folds. In this paper, preliminary results are provided that refer to tests performed by 13 Italian singers, which were equipped with a contact microphone and a microphone in air. A first objective assessment of the effects of SOVTE on the vocal performance has been made through the estimation of acoustic parameters extracted from the recorded vocal signals and the comparison of these parameters before and after the SOVTE. The main outcomes are an increase of the energy in the medium frequency-range (from 1 kHz to 4 kHz), the Singing Power Ratio and the Cepstral Peak Prominence Smoothed. Furthermore, an increase in the voice-production efficiency has been estimated by comparing the intensities of the signal in air to the signal at the output of the contact microphone.