Speaker-Oriented Classroom Acoustics Design Guidelines in the Context of Current Regulations in European Countries

Abstract

Summary Most European countries have regulatory requirements or guidelines for reverberation time in classrooms which have the goal of enhancing speech intelligibility and reducing noise levels in schools. At the same time, school teachers suffer frequently from voice problems due to high vocal load experienced at work. With the aim of improving working conditions for teachers, this article presents guidelines for classroom acoustics design that meet simultaneously criteria of vocal comfort and speech intelligibility ,w hich may be of use in future discussions for updating regulatory requirements in classroom acoustics. Tw or oom acoustic parameters are shown relevant for as peaker: the voice support, linked to vocal effort, and the decay time derive df rom an oral-binaural impulse response, linked to vocal comfort. Theoretical prediction models for room-averaged values of these parameters are combined with am odel of speech intelligibility based on the useful-to-detrimental ratio and empirical models of signal-to-noise ratio in classrooms in order to derive classroom acoustic guidelines, taking into account physical volume restrictions linked to the number of students present in ac lassroom. The recommended values of reverberation time in fully occupied classrooms for flexible teaching methods are between 0.45 sa nd 0.6 s( between 0.6 and 0.7 si na nu noccupied bu tf urnished condition )f or classrooms with less than 40 students and volumes belo w2 10 m 3 .W hen designing larger classrooms, ad edicated acoustic study taking into account considerations about geometry ,m aterial and speaker/audience placements should be made, which can help to increase the voice support and reduce the vocal effort.