THE EFFECT OF RELATIVE-HUMIDITY OF INHALED AIR ON ACOUSTIC PARAMETERSOF VOICE IN NORMAL SUBJECTS

The hypothesis that relative humidity (RH) of air exerts an effect on voice has been widely accepted. The aim of this study has been to asse ss whether this can be demonstrated. Eight healthy subjects inhaled du ring ten minutes three different air conditions: dry, standard room, a nd humidified air. After inhalation, the subjects produced repeatedly a sustained /a/ of controlled pitch and loudness, which was analyzed f or perturbation and noise-to-harmonic parameters. Perturbation measure s increased after inhalation of dry air. No significant differences ex isted between standard and humidified air. No significant difference i n the noise-to-harmonic ratio was found among the three conditions. We conclude that the human voice is very sensitive to decreases in RH of inhaled air, because even after a short provocation with dry air, a s ignificant increase in perturbation measures was found.