Working-day effects on the spectral characteristics of teaching voice

Ten teachers made recordings during one normal working day using a portable DAT recorder and a head-mounted microphone. In addition, the subjects fill ed in a questionnaire of signs of vocal fatigue. The speech samples were se lected from the first and last lesson from three points representing the be ginning, middle and end part of the lesson, respectively. To standardize th e samples, 30 [a] vowels from stressed syllables were chosen for spectral a nalysis. The level of the fundamental and second formant regions (L1), the level off frequency ranges 2-5 kHz (L2) and 5-10 kHz (L5) were measured. Fr om these measurements the parameters L1-L0, L1-L2 and L1-L5 were formed and used in the analyses as well as the energy levels below and above 1 kHz (a lpha). Statistically significant changes were observed in the following par ameters: the L1-L2 and L1-L5 differences, and the a ratio. In general, ther e was an increase in the energy content of the high frequency components du e to vocal loading. The subjective reports revealed a statistically signifi cant relationship with the spectral characteristics.