Spectral moment analysis of unilateral vocal fold paralysis.

Many acoustic measures have been used to assess and track the voices of patients with voice problems. Some of these measures rely on the accurate measurement of fundamental frequency to produce reliable results. Patients with voice disorders often produce voices with considerable quasiperiodicity or aperiodicity. There are other measurements that do not depend on the accurate tracking of fundamental frequency by computing the spectrum of the sound and comparing different parts of the spectrum. The moments of the spectral distribution may also be important measurements to use in patients with voice problems. Several studies have reported good results using these measures to track treatment progress. In this study, spectral moments were used to assess the effectiveness of two treatment approaches in patients with unilateral vocal fold paralysis (UVFP). Twenty-six patients with UVFP and dysphonia (16 female and 10 male patients) were studied. Thirteen underwent surgery to improve their voice, whereas the other 13 received voice therapy. The patients were recorded at three time intervals: before the start of treatment, about 1 month after treatment has been completed, and at 3 months after treatment. They produced three types of speech material, vowels /ah/ and /oo/ and a simple sentence. The first four spectral moments (mean, standard deviation, skewness, and kurtosis) were computed from the long-term average spectrum. Severity of voice dysphonia was rated on a 11-point scale ranging from 0 (normal) to 10 (aphonic). There were no statistical differences between males and females for any of the four moments. There was also no difference between the two treatment types. There were differences among the three types of speech material for moments 1 and 3. There were also differences for moments 1, 2, and 3 for the three treatment conditions with most of the differences occurring between the pretreatment and first posttreatment condition. Severity of dysphonia decreased significantly from the pretreatment to either of the two posttreatment conditions. Spectral moments appear to be viable acoustic measurements to use to assess the effects of treatment on the voice of patients with UVFP.