Long-term vocal parameters of primary school teachers and classroom acoustics with and without an acoustical treatment

The main purpose in classroom design is to facilitate learning practice by ensuring a good level of speech communication. It has already been proved that high reverberation or excessive noise levels in schools do not allow a proper communication between teachers and pupils. Furthermore, when classroom acoustics is poor, vocal health of teachers may be compromised. This study aims at investigating the effects of acoustic treatments in two primary schools in Italy, one in Torino and one in Bolzano. Measurements were carried out before and after a low-cost intervention both in occupied and unoccupied conditions, in Torino, monitoring the vocal activity of two teachers. In Bolzano, the effect of different acoustic conditions on one female teacher who teaches in treated and not treated classrooms was studied. Vocal long-term monitoring were conducted in the two locations for 3 to 4 working days, before/without and after/with the acoustic treatment of classrooms, using Voice-Care, a new portable vocal analyzer developed at the Politecnico di Torino. This research led to identify four main focuses: (1) variation in background noise level during frontal lessons, (2) change in classroom acoustics (reverberation time, clarity, room gain, voice support), (3) change in the use of voice in terms of variation of mean sound pressure level at 1 m from the teacher's mouth (SPLm,1m), mean fundamental frequency (F0,m) and phonation time percentage (Dt%), (4) improvement of speech intelligibility through the measurement of the speech transmission index for public address (STIPA). The subjective impression, investigated through questionnaires, gave encouraging results on the perception of sounds and voice when an acoustic treatment was present in classrooms. Answers were organized in a database which easily allows to correlate the subjective impression with the activity and the measured data