Background: Adductor laryngeal dystonia (ADLD) is a focal dystonia characterized by intermittent, involuntary overclosure of the vocal folds during speech. One defining characteristic of ADLD is task-specificity: certain vocal tasks increase symptom expression. Previous studies have shown that voice severity in ADLD is increased during production of sentences loaded with voiced compared to voiceless phonemes (Erickson, 2003; Roy et al., 2007). Therefore, researchers propose that auditory-perceptual assessment in ADLD include specific sentence stimuli (Dedo & Shipp, 1980). Many clinicians use the Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V; Kempster et al., 2009), which also includes sentences with voiced- and voiceless-loaded phonemes. Whether these short CAPE-V sentences are equally effective at evoking symptoms as the longer sentences included in previous ADLD research is unknown.
Objectives: The purpose of this study was to determine the effect of phonetic loading and sentence length on symptom expression in ADLD speakers by comparing longer all-voiced and voiceless-loaded sentences used in previous research with CAPE-V sentences.
Methods/Design: Fifty speakers with ADLD (16 AMAB; 34 AFAB; Average age = 60 years) produced 30-syllable and 8-syllable (CAPE-V) all voiced sentences and 26-syllable and 6-syllable (CAPE-V) voiceless-loaded sentences. Speakers were recorded using research quality equipment, and samples were peak normalized. Fifteen novice listeners will listen to each speech sample in random order and rate overall voice quality severity using 100-mm visual analog scales. Twenty percent of samples will be repeated to assess intra-rater reliability. Inter-rater reliability also will be calculated. Repeated measures ANOVA will be used to determine the effect of phonetic loading (voiced versus voiceless-loaded), sentence length (long versus short), and their interaction on perceived voice severity.
Results: It is predicted that there will be a main effect of phonetic loading, with all voiced sentences being perceived more severely than voiceless-loaded sentences. We also anticipate an interaction between phonetic loading and sentence length, with greater severity differences between all-voiced and voiceless-loaded stimuli for longer compared to shorter sentences.
Conclusion: Results will help determine the effect of phonetic loading by sentence length on symptom expression in ADLD. Results have clinical implications for current standardized auditory-perceptual voice assessment measures.