Vocal impact of a prolonged reading task at two intensity levels: objective measurements and subjective self-ratings.

OBJECTIVES The objectives of this study are to evaluate the impact on voice of both duration and intensity level of 2 hours of continuous oral reading. Voice modifications accompanying changes in intensity level during prolonged reading tasks are analyzed. METHODS Fifty normophonic women undergo two sessions of voice loading in which the required intensity level of voice varied between 60-65 dB(A) for the first session and 70-75 dB(A) for the second session. The effects of loading on objective data (average fundamental frequency [F0], jitter%, shimmer%, noise-to-harmonic ratio, maximum phonation time, lowest frequency [F-Low], highest frequency [F-High], frequency range [Range], lowest intensity [I-Low] level, and highest intensity level) and self-ratings (voice quality, phonation effort, vocal fatigue, and laryngeal discomfort) are assessed every 30 minutes during the loading tasks. RESULTS Results indicate that average F0, F-Low, I-Low, maximum phonation time, feeling of phonation effort, vocal fatigue, and laryngeal discomfort increase during prolonged reading, whereas shimmer% and self-rating of voice quality decrease. Average F0, F-High, and Range are the only parameters influenced by the required intensity of vocal load; they are significantly higher in the 70- to 75-dB session compared with the 60- to 65-dB session. Concerning the subjective self-ratings, similar results for the four ratings used suggest that only one would suffice in future studies. CONCLUSIONS These results confirm the importance of both duration and intensity level as loading factors, even if intensity level affects fewer variables than duration.