Vowel harmonic amplitude differences in persons with vocal nodules

Background: Spectrum is a fast Fourier transform-generated power spectrum extracted from the speech sample. It is reported to provide a quantitative acoustic index of the degree of glottal abduction and adduction in voices perceived to be breathy or pressed. In the present study, it was hypothesized that there would be abnormal reduction of higher harmonic amplitudes relative to the amplitude of the first harmonics in the subjects with vocal nodules and hence the present study was carried out. Method: One hundred twenty 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 (H1 and H2) as well as the harmonics at the first, second, and third formants (A1, A2, and A3) using the Computerized Speech Science Lab (Kay Pentax, Lincoln, NJ). Results: There was a significant difference between the means of two groups for all the parameters, such as H1-H2, H1-A1, H1-A2, and H1-A3 at P < 0.05. The obtained results are discussed with respect to the underlying pathophysiology. Conclusions: The present study investigated the vowel harmonic amplitude differences in persons with vocal nodules. The results revealed a significant difference between the two groups for the vowel harmonic amplitude differences. This particular measure could be used to track the changes following the vocal treatment.