Harmonic Amplitude Differences and Perceived Voice
Quality in Adductor Spasmodic Dysphonia

M Cannito, L Chorna, E Buder, T Murry, G Woodson


Harmonic amplitude difference measures (H1-H2, H1-A1, H1-A2, H1-A3) were obtained from vowel nuclei of spoken words produced by sixteen speakers with adductor spasmodic dysphonia (ADSD) before and after botulinum toxin injection of the vocal folds, and by six normal speakers. In addition, perceptual scaling judgments of the speakersí degree of roughness and breathiness were completed by six listeners with expertise in voice disorders. Normal controls exhibited expectedly large differences between H1 and higher harmonics, but pre-injection ADSD exhibited the smallest differences, suggestive of short open quotients. Following injection, ADSD harmonic values shifted in the direction of normalcy but did not attain normal levels. The three speaking conditions were significantly different for all measures. Correlations of each harmonic amplitude measure with voice quality judgments were statistically significant and were in the directions expected on the basis of prior literature for normal, simulated and synthesized abnormal voice qualities. That is, roughness positively correlated with harmonic amplitude differences, while breathiness was negatively correlated. The present findings demonstrate the applicability of harmonic amplitude difference measurement for characterizing significantly pathologic voices and documenting treatment related change. Specific physiological implications of these findings will be discussed.