Changes in voice and subjective sensations during a 45-min vocal loading test in female subjects with vocal training

Twenty-four females (mean age 38 years) with varying amounts of vocal training read aloud from a book for 45 min (70 dB at 40 cm distance). Symptoms of the throat and voice were ascertained with a questionnaire before, during and after the test. Fundamental frequency (F(0)) and sound pressure level (SPL) were measured. The alpha ratio describing the spectrum slope was calculated: SPL in the range 1-5 kHz minus SPL in the range 50 Hz-1 kHz. All measurements were made for the 1st, 5th, 15th, 30th and the 45th min of loading and for text reading before and after it. F(0), SPL and alpha values rose during the test, which may indicate adaptation to loading. During the first 5 min, however, these parameters showed a decreasing tendency, possibly reflecting warm-up. Subjects with more vocal training had a lower F(0) in the loading test. SPL seemed to reflect variation of symptoms during loading. Changes in acoustic parameters did not distinguish between subjects with most and fewest symptoms of fatigue in this test.