Vocal loading-related changes in male teachers' voices investigated before and after a working day

Vocal loading-related changes have mainly been investigated in female voice users. The present study investigated male teachers' voices before and after a working day. A questionnaire was used to select 22 male teachers as subjects from a larger group. Ten reported suffering often from symptoms of vocal fatigue (MC = multiple complaints group), 12 reported few vocal complaints (FC group). The subjects recorded a text reading sample at habitual loudness and loudly, and sustained vowel [a:] before and after an approximately 6-hour working day. Text samples were analyzed for total sound pressure level (SPL) and SPL at three frequency regions (50-1,000 Hz, 1-2 kHz, 2-5 kHz), fundamental frequency (F0) and alpha ratio [(SPL 1-5 kHz) - SPL (50 Hz-1 kHz)]. Jitter and shimmer were calculated from the vowel. The subjects filled in a questionnaire about vocal sensations. The MC group reported more symptoms of vocal fatigue, and the symptoms increased during the working day. F0 and SPL increased in both groups. Alpha ratio increased in the MC group but remained the same in the FC group. The MC group had higher values of jitter and shimmer. Jitter diminished in the FC group but did not change significantly in the MC group. The differences between the groups reflect either different strategies for coping with vocal loading or different loading-induced changes in the vocal organ.