Acoustic voice analysis in patients with essential tremor

To quantify several acoustic features of the voice in patients with essenti al tremor (ET). 28 patients and 28 age- and sex-matched controls were studi ed. ET severity was assessed with the rating scale for tremor of Fahn, Tolo sa, and Marin. The Computerized Speech Lab 4300 program (Kay Elemetrics) wa s used. Two-second samples of a sustained /a/ and a sentence were captured with a microphone and laryngograph equipment. Measures included fundamental frequency (F-0), frequency perturbation (jitter, Koike algorithm), intensi ty perturbation (shimmer, Horii algorithm), and harmonic-to-noise ratio (H/ N, Yumoto algorithm) of the vowel /a/. and the frequency and intensity vari ability of the sentence, phonational range, and dynamic range at the natura l frequency, maximum phonational time, and s/z ratio. All subjects underwen t indirect laryngoscopy and/or laryngeal fibroscopy. When compared with con trols, ET patients showed higher jitter, lower H/N ratio (the last one only with laryngographic signal). of the vowel /a/, lower frequency variability in the microphonic signal, lower intensity variability in the laryngograph ic signal of the sentence, and significantly lower dynamic range at natural frequency of phonation. ET patients reported higher frequency of the prese nce of high voice intensity, tremor, and struggle. Several acoustic paramet ers were influenced by the severity of the disease, including shimmer, jitt er, H/N ratio, frequency variability of the sentence, and s/z ratio, althou gh neither of the acoustic analysis values or the phonetometric measurement s were affected by the presence of voice tremor or by a successful pharmaco logical treatment of ET.