Disfluency in spasmodic dysphonia: a multivariate analysis.

This study examined visual analog scaling (VAS) judgments of disfluency by normal listeners in response to oral reading by speakers with spasmodic dysphonia (SD) and by nondysphonic controls, as well as the variables of frequency of occurrence of disfluencies, speaking rate, number of reading errors, and temporal acoustic measures of interword interval duration and articulation time. MANOVA yielded statistically significant differences between SD and control speakers for all variables except reading errors. Although no significant fluency-related differences were observed in terms of type of vocal spasm or voice tremor, significant differences in disfluency measures were obtained for clinical ratings of severity of dysphonia. Greater dysphonia severity ratings were associated with decreased fluency, but milder ratings were not necessarily associated with disfluency. Stepwise multiple regression analysis demonstrated that frequency of disfluency occurrence, speaking rate, and reading errors accounted for more than three fourths of the variability in VAS judgments of disfluency. Findings suggest that although disfluency is not a defining feature of SD, it does contribute significantly to the overall clinical impression of severity of the disorder.

Measuring the strength of auditory fusion for synchronously and nonsynchronously fluctuating narrow-band noise pairs.

This experiment examines the "strength" of auditory fusion for narrow-band noise pairs. Each pair of noise bands consisted of a target band and a flanker band presented simultaneously. The temporal envelopes of the noise bands within a pair fluctuated either in synchrony (synchronous condition) or not in synchrony (nonsynchronous condition). Each noise-band pair was alternated rapidly with a noise band (captor band) presented alone. The duration of the silent period between a noise-band pair and a captor band [i.e., onset-to-onset interval (OTO)] was decreased by listeners until auditory fusion of the pair was disrupted by capturing the target band into a sequential-stream with the captor band. Results showed that listeners required significantly shorter OTOs to capture the target bands from the synchronous pairs than from the nonsynchronous pairs, suggesting that strength of auditory fusion was greater for the noise bands that fluctuated in synchrony than for those that did not. The results of this experiment are discussed relative to hypotheses based on auditory stream segregation to explain auditory phenomena such as comodulation detection difference, modulation detection interference, and comodulation masking release.

The effects of perceived motion on sound-source lateralization.

Lateralization of dichotic click pairs differing in time of onset was studied under conditions of angular acceleration, optokinetic stimulation, and gaze fixation. Data obtained from 20 subjects with normal hearing indicate poorer left-right judgment performance for small time differences, as well as shifts in subjective simultaneity, for all experimental conditions relative to control conditions. In addition, response times increased for the experimental conditions. The results suggest that real or apparent motion may affect an individual's ability to process one of the major cues for sound-source localization--binaural time difference--under conditions similar to those encountered in vehicular motion.