Optimal acoustic conditions in classrooms

Computer models of eight classrooms were constructed with varying combinations of absorbent materials on the surfaces of the rooms using the CATT 7.0 computer program. The amount, location and cost of finish materials and the noise levels produced by the air-conditioning system were varied in the models. RASTI values were calculated for six seats in each room. By determining conditions that result in maximum RASTI values, maximum speech intelligibility conditions were obtained. Background noise levels dominated the RASTI values at levels of NC 40 and higher regardless of room finishes. At RASTI values of NC 35 and less, once an amount of absorbent material equal in area to the floor was present, only small changes in RASTI values were observed whether the material was located on the ceiling or the upper parts of the walls or a combination of both. The cost of material and locations of typical furnishings were also considered in the process.