Changes in Voice Quality after a Pure Tone Stimulation (PTS) Program

Abstract

Introduction. Auditory feedback allows individuals to monitor their vocal characteristics and adjust to maintain optimal voice quality. One type of auditory stimulation for conversational voice training/therapy is pure tone stimulation. This technique presents binaural auditory stimuli consisting of pure tones separated by half-step intervals to modify the fundamental frequency of the speaking voice and expand the vocal range. Objectives. This study aimed to characterize detectable changes in voice production following the application of pure tone stimulation (PTS) among speakers with and without voice disorders. Methods. Data from thirty-nine participants (28 individuals with voice disorders and 11 individuals with normal voices) were analyzed for this study. All participants engaged in binaural PTS exercises. Participants recorded a sustained vowel /a/ before and after the PTS exercises. Multiple acoustic voice parameters were extracted from the sustained vowel samples (fundamental frequency, pitch strength, harmonics-to-noise ratio, and smoothed cepstral peak prominence). Additionally, a visual analogue scale (VAS) interpretation of narrowband (NB) spectrograms was conducted to assess voice quality. Results. Statistically significant increases in fundamental frequency were found after the PTS exercises, except for males in the normal voices group. Pitch strength increased after the PTS, regardless of gender. Participants also demonstrated an increase in the harmonics-to-noise ratio. VAS ratings of NB spectrograms indicated improvement in voice quality following the program. Conclusions. Voice changes after performing PTS suggest voice quality improvement, as measured by acoustic analysis of vowel production and qualitative assessment of NB spectrograms among participants with and without voice disorders.