Ambient noise levels and reverberation times in Mississippi school rooms

Abstract

Nine elementary school classrooms at three Mississippi public schools were selected at random for noise and reverberation time measures to monitor voluntary compliance with ANSI standard S12.60-2002 (Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools). One-hour equivalent dBA noise levels and reverberation times (T60) were measured with SpectraPLUS Version 5.0 software. Measures were taken on separate days at each school in unoccupied classrooms with the HVAC system operating. For ambient noise measures an Audix TR40 omnidirectional microphone was placed in a 12 inch stand on a student's desk near the middle of the room and oriented toward the teacher's desk at a 45 degree angle. For the reverberation time measure a 400 watt loudspeaker (Yamaha BR15M) was placed on the teacher's desk about 3 meters from the microphone. Results showed that noise levels varied from 28 dBA to 51 dBA with broad spectra containing peaks at 120 Hz and harmonics. Five of nine classrooms had noise levels that exceeded the ANSI recommended level of 35 dBA. Reverberation times varied from .21 to .62 seconds; only one classroom exceeded the recommended minimal reverberation time of .6 seconds. Acoustical modifications to reduce noise levels and reverberation times will be addressed. © 2011 Acoustical Society of America.