The Vocal Impact of a Prolonged Reading Task at two Intensity Levels

The purpose of this study is to evaluate the impact on voice of both duration and intensity level of 2 hours of continuous oral reading. Fifty normophonic women (mean age: 25.4 years) undergo two sessions of voice loading in which the required intensity level of voice varied: 60-65 dB(A) for the first session, and 70-75 dB(A) for the second session. The results of loading are assessed with regard to objective data and self-rating of voice obtained every 30 minutes during the oral reading tasks. Serial voice quality objective data is obtained by use of Multi-Dimensional Voice program (Average fundamental frequency (AvF0), Jitter percent (Jitt), Shimmer percent (Shim), Noise-to-Harmonic Ratio (NHR)). Serial measurements of maximum phonation time (MPT) and voice range are carried out by use of Kay Elemetrics Computerized Speech Lab. The following characteristics are also categorized by the use of a 100 mm visual analogue scale every 30 minutes of the oral reading tasks: voice quality, feeling of phonation effort, vocal fatigue, and laryngeal discomfort.
Results indicate that AvF0, lowest frequency of voice range, softest output of phonation, feeling of phonation effort, vocal fatigue and laryngeal discomfort rise during prolonged oral reading. On the contrary, Shim and self-rating of voice quality decrease significantly with the passage of time during the voice loading. Jitt and NHR tend to decrease. MPT decreases after the first 30 minutes but increases afterwards. AvF0 and highest frequency of voice range are the only parameters influenced by the required intensity of oral reading task: these values are significantly higher in the 70-75 dB session compared to the 60-65 dB session.