Acoustics and perception of wet vocal quality in identifying penetration/aspiration during swallowing

The present study is an investigation into the association between "wet" vocal quality and prandial material in the larynx during phonation. The presence of such prandial material is indicative of oropharyngeal dysphagia and results from entry of material into the laryngeal vestibule during swallowing. The study has two primary aims: (1) to assess whether acoustic parameters can signify prandial material in the larynx during phonation; (2) to determine whether clinicians reliably perceive a "wet" vocal quality when this condition occurs. Results show that material in the larynx produces reliable acoustic consequences, including elevated measures of perturbation and signal noise and reduced amplitude of H1 relative to H2. Also, it can generate a characteristic frequency and amplitude modulation in the sound pressure waveform that is highly specific to the presence of material in the larynx during phonation. Results further show that "wet" vocal quality is not reliably perceived by clinicians when material is in the larynx during phonation, and that there is a high degree of interrater variability for perceptual judgments of "wetness". Overall, acoustic information can be useful in the clinical identification of individuals with penetration or aspiration during swallowing, and it is more reliable in detecting this condition than perceptual judgments of vocal quality. Results also indicate that there is likely to be more than one voice quality percept associated with material in the larynx, and that clinician training might increase the accuracy and reliability of perceptual judgments.