Acoustic prediction of severity in commonly occurring voice problems.

The relative effectiveness of three acoustic measures (jitter, shimmer, and harmonic/noise ratio) in predicting the dysphonic severity of a diverse clinical population singly and together was investigated. Phonatory samples were recorded from 20 normal subjects and 60 patients representing 3 laryngeal groups (nodules, paralysis, and functional). The phonatory samples were evaluated by 22 listeners using a 7-point equal-appearing interval scale. Shimmer produced a bivariate correlation of 0.54 with dysphonic severity; harmonic/noise ratio correlated -0.32 with dysphonic severity; and jitter produced no significant correlation with severity. The combination of acoustic variables through multiple regression analysis produced a correlation of 0.56, with only shimmer and average F0 contributing to the correlation. For this particular clinical population, therefore, findings indicated that (a) none of the variables was strongly correlated with dysphonia ratings, and (b) a combination of acoustic predictors was no more successful than a single predictor of dysphonic severity, namely, shimmer.