Variability analysis of Fo parameter in the voice of individuals with hearing disturbances.

The material of this investigation comprised a group of 18 patients with deep hypoacousis (over 70 dB) or complete deafness which, depending on the onset of the deafness, was divided into the 3 categories: congenital, early childhood to 3rd year of life, and postlingual. All of them underwent ENT, phoniatric and stroboscopy examinations; in 10, X-ray tomography of the larynx was also performed. The status of hearing ability was assessed by audiometric examinations using pure tones in air and bone conductions. The acoustic examinations comprising spectrographic and tonographic analyses were performed on an appropriate linguistic material including vowels, isolated words, sentences and reading text. The measurement of Fo was performed on isolated vowels. In order to characterise the degree and kind of periodicity disturbances the following parameters were estimated: the medium value of fundamental frequency, the range of Fo variability, the maximal change of period length from cycle to cycle, and its medium value (jitter). The results of the acoustic examinations revealed different degrees and kinds of periodicity disturbances depending on the depth of the hypoacousis and its onset.