Aerodynamic and acoustic voice measurements of patients with vocal nodules: variation in baseline and changes across voice therapy.

An important clinical issue concerns the efficacy of current voice therapy approaches in treating voice disorders, such as vocal nodules. Much research focuses on finding reliable methods for documentation of treatment results. In this second treatment study of ten patients with vocal nodules, who participated in a behaviorally based voice therapy program, 11 aerodynamic (transglottal air pressure and glottal waveform) and acoustic (spl, f0, and spectrum slope) measures were used. Three pretherapy baseline assessments were carried out, followed by one assessment after each of five therapy phases. Measurements were made of two types of speech materials: Strings of repeated /pae/ syllables and sustained /ae/ phonations in two loudness conditions: comfortable loudness and loud voice. The data were normalized using z-scores, which were based on data from 22 normal subjects. The results showed that the aerodynamic measures reflected the presence of vocal pathology to a higher degree than did the acoustic spectral measures, and they should be useful in studies comparing nodule and normal voice production. Large individual session-to-session variation was found for all measures across pretherapy baseline recordings, which contributed to nonsignificant differences between baseline and therapy data.