Acoustical Quality in Educational Buildings : Measurements in Brazilian Public Schools

The importance of good acoustical quality in schools has been widely discussed in scientific media. It is undeniable that proper acoustical features influence student achievement. After studying architectural characteristics of schools and subjective data from students and teachers presented in former meetings, this paper presents the results of an acoustical measurement evaluation of schools in Southern Brazil. It was measured the background noise levels (Leq(a)3min), reverberation times (RT) and early decay times (EDT), of five standard schools types. The results of Leq(a)3min are above the recommended limits of several international standard in all of five schools. The results range from 51.5 to 70.5 dB(A). Considering the recommended signal-to-noise ratio of +15 dB(A) to obtain good intelligibility, in the worse case the teacher would have to raise his voice to 80.5 dB(A), value that he might bring him vocal problems. The RT and EDT values are also above the recommended 0.5 seconds and the results range from 1.15 to 1.68 seconds for RT and from 0.83 to 1.30 seconds for EDT. The correlation of Leq(a)3min and S/N Ratio with reverberation times, as proposed by Bradley, the result for the school with best acoustical condition indicates a level of intelligibility of 88%. The result can be considered poor since this is the best condition in the classroom and also because it is desired values as close as possible to 100%.