Leena M. Rantala

The aim of the study was to research associations between classroom acoustic parameters and teachers' voice use and vocal health (N = 40). From voice samples, sound pressure level (SPL), fundamental frequency ( F ₀ ), and the tilt of spectrum slope were analysed. Information on voice symptoms was collected by means of questionnaires. Room acoustic variables were reverberation times (T ₆₀ , EDT), sound attenuation (DL ₂ ) and parameters measuring how well speech is perceived (C ₅₀ , D ₅₀ , STI). The associations between the variables were studied for the whole group and separately for quiet and noisy classrooms. The results showed that all the room acoustic variables measured correlated with a teacher's voice variables. Voice SPL was influential especially in the noisy classrooms and F ₀ in the quiet classes. A teacher's vocal health was poorer if the room acoustic variables indicated better listening conditions. The findings suggest that good listening conditions do not necessarily imply good speaking conditions in classrooms.

Purpose: The aim of this study was to research the associations between noise (ambient and activity noise) and objective metrics of teachers' voices in real working environments, i.e. classrooms. Method: Thirty-two female and eight male teachers from 14 elementary schools were randomly selected for the study. Ambient noise was measured during breaks in unoccupied classrooms, likewise the noise caused by pupils' activity during lessons. Voice samples were recorded before and after a working day. Voice variables measured were sound pressure level (voice SPL), fundamental frequency (F₀), jitter, shimmer, and the tilt of the sound spectrum slope (alpha ratio). Results: The ambient noise correlated most often with the F₀ of males and voice SPL, while activity noise correlated with alpha ratio and perturbation values. Teachers working under louder ambient noise spoke more loudly before work than those working in lower noise levels. Voice variables generally changed less during work among teachers working in loud activity noise than among those working in lower noise levels. Conclusions: Ambient and activity noises affect teachers' voice use. Under loud ambient noise teachers seem to speak habitually loudly and under loud activity noise levels teachers' ability to react to loading deteriorates.

Objective: The aim of the study was to investigate if voice ergonomic risk factors in classrooms correlated with acoustic parameters of teachers’ voice production. Methods: The voice ergonomic risk factors in the fields of working culture, working postures and indoor air quality were assessed in 40 classrooms using the Voice Ergonomic Assessment in Work Environment – Handbook and Checklist. Teachers (32 females, 8 males) from the above-mentioned classrooms recorded text readings before and after a working day. Fundamental frequency, sound pressure level (SPL) and the slope of the spectrum (alpha ratio) were analyzed. Results: The higher the number of the risk factors in the classrooms, the higher SPL the teachers used and the more strained the males’ voices (increased alpha ratio) were. The SPL was already higher before the working day in the teachers with higher risk than in those with lower risk. Conclusion: In the working environment with many voice ergonomic risk factors, speakers increase voice loudness and use more strained voice quality (males). A practical implication of the results is that voice ergonomic assessments are needed in schools.