Measurement of the ambient noise level, reverberation time and transmission loss for classrooms in a public school

The acoustical quality of classrooms in Brazilian public schools is evaluated. Reverberation time (RT) was measured in classrooms according to ISO 3382. Measurements have shown that empty classrooms display an RT of 1.6 s at 500 Hz. Ambient noise of the classrooms was also evaluated according to the Brazilian Standard for Acoustical Comfort NBR 10152 and the British Building Bulletin BB93. The walls separating the corridor and the classrooms have high level louvers, with fixed glass slats which provide a permanent opening for ventilation and illumination, and one door. The measured weighed apparent sound reduction index R' w , (ISO 717-1) for these walls was R' w = 13 dB. This is a very low value, when confronted with those demanded, for example, by the German Standards DIN 4109-"Noise Control and Building", and DIN 18041-"Acoustical quality in small to medium-sized rooms" (R 'w =31 dB).