Correlates of varying vocal fold adduction deficiencies in perception and production: methodological and practical considerations.

In this study the voice characteristics of normal male and female speakers are compared to those of two groups of patients with unilateral vocal fold paralysis. In order to enhance phonation, the patients in the first group compensate for the adduction deficiency which results from paralysis. The patients in the second group do not use compensatory strategies. Sustained vowels [i:, a:, u:] were produced by the speakers and scored for roughness, breathiness and hoarseness (RBH) by 8 raters. Although interrater agreement for RBH scores is only moderate on average, these percepts make consistent distinctions between the three speaker groups. Consistent but different distinctions are made between the three speaker groups for male and female speakers. The results show that male and female speakers should not be pooled in experimental studies of the pathological voice. Our results also indicate that female patients with a compensated unilateral vocal fold paralysis cannot be clinically evaluated solely on the basis of perception, because their voices cannot be distinguished from normal, healthy female speakers, despite their physiological impairment. The group distinctions made on the basis of RBH scores are supported by differences in the acoustic parameters which are derived by automatic analysis of the sustained vowels. Despite identical group distinctions for RBH scores and acoustic parameters, the acoustic basis of the percepts is not straightforward. Different acoustic predictors of the percepts were found for male compared to female speakers. Additionally, interrater differences point towards the presence of perceptual trading relations.