Changes in teachers' speech during a working day with and without electric sound amplification

An increase in fundamental frequency (F(0)) and in sound pressure level (SPL) has been reported both after vocal loading tests and after a teacher's working day. This increase has been found to be greater among teachers with fewer voice complaints. The present study investigated speech changes during a teacher's working day (a) in ordinary conditions and (b) when using electric sound amplification while teaching. Five Icelandic teachers (mean age 51 years) volunteered as subjects. Classroom speech was recorded with a portable DAT recorder and a head-mounted microphone first in ordinary conditions, and the next week while using electrical sound amplification. Recordings were made during the first and the last lesson of the hardest working day of the week. F(0) and SPL were analyzed. The subjects' comments were gathered by questionnaire. An increase in F(0) and SPL was found during the working day in both teaching conditions but the change was larger and for F(0) statistically significant when amplification was used. All 5 teachers reported less tiredness of the vocal mechanism when using amplification. The results support the suggestion that a vocal loading-related increase in F(0) and SPL is not merely a sign of vocal fatigue but may even reflect an adequate adaptation to loading. Situational factors cannot be ignored, however.