Determination and Comparison of Range – Average and Perturbation of Basic Frequency in Addition to Intensity Disturbance in the Voice of the Patients with Unilateral Vocal Fold Paralysis and Normal Persons

AbstractIntroduction: Vocal fold paralysis is one of the relatively prevailing damages causing voice disorder. There is little knowledge about how it impacts different features of people voice. Now it assumes that laboratory measurements may reveal the effects of this complication arising voice disorder.As, there are not authenticated acoustic measures in Iranian Population the voice of affected individuals is compared with the normal persons in this study.Methods: In a descriptive - analytical and cross - sectional study 10 male patients of based hospital affected by vocal fold paralysis were monitored and some of acoustic traits of their voice were compared with the control group by use of DR. SPEECH software. The results were analyzed by independent t-test.Results: There were no significant differences in average and extent of frequency alterations during reading sentences. The average of basic frequency perturbation and intensity disturbance in two groups were significantly different.Conclusion: Any damage to vocal folds makes them asymmetric which in turn vibrate two vocal folds with different pitch resulting in two different basic frequencies. Therefore noises arise in patient voice. These noises in our samples were appeared in high frequencies due to increase of maximum basic frequency which this later enhances mean of basic frequency of patient voice.High pitch extent of basic frequency alterations is the result of difference in voice box mechanisms. Frequency disturbance is due to momentary and involuntary changes in vocal system which appears in damaged larynges and asymmetric vocal folds.Vocal pitch perturbation as a sudden involuntary change in sound intensity is affected by sub-glottal air pressure. This pressure is poorly controlled due to injured vocal folds which cause sudden changes in voice intensity.Keywords: Basic frequency, range of basic frequency alterations, basic frequency perturbation, intensity disturbance, unilateral vocal fold paralysis