Vowel Harmonic Amplitude Differences in Individuals with Unilateral Vocal Fold Paralysis

Abstract

Background: The studies reviewed suggest the potential clinical applications of vowel harmonic amplitude differences. In this study, it was hypothesized that there would be abnormal reduction of higher harmonic amplitudes relative to the amplitude of the first harmonics in individuals with unilateral vocal fold paralysis (UVFP) as they are characterized by breathy voice due to inadequate closure of vocal folds. Method: A total of 80 participants were divided into clinical group and control group. They were instructed to phonate/a/at their most comfortable pitch and loudness. Fourier transformation of the recorded acoustic signal was first performed to create a spectrum. Amplitudes were measured for the first and second harmonics as well as the harmonics at the first, second, and third formants using the Computerized Speech Science Lab. Results:Independent t-test was employed to compare the significant differences between the clinical and the control group in both males and females. The results revealed significant differences across the two groups and gender at P < 0.05. The obtained results were discussed with respect to the underlying pathophysiology. Conclusion: Spectral deviations in the clinical group are explained due to the presence of phonatory gap due to the UVFP.