A basic protocol to characterize classroom acoustics of primary-schools

With the aim to promote a fast and effective characterization of the sound environment in educational facilities and an adequate classroom acoustics design, this work provides a basic measurement protocol which consists of a minimum number of parameters and positions to be considered. The present study involved 29 primary-school classrooms where background noise level during silent and group activities, reverberation time, speech clarity, useful-to-detrimental ratio and speech levels have been acquired in occupied condition along the main axis and in one or two offset positions. Two cut-off values of maximum reverberation time to ensure optimal acoustic conditions in the case of moderate and severe requirements, respectively, were assumed equal to 0.8 s and 0.6 s, according to literature and subjective data. For each cut-off value, classrooms were divided in two consistent groups either if they were compliant or non-compliant with such requirements, respectively. Given the strong correlation among the measured quantities, cut-off values were also identified for the other acoustical parameters. The main result of the work suggests that more convenient parameters, such as clarity in the central location of the classroom, can be used beyond reverberation time, which implies a more laborious measurement procedure.