Optimization of the acoustic treatments in order to achieve the Italian minimum environmental criteria (CAM) for classrooms

Abstract

A recent Italian legislation has established the Minimum Environmental Criteria (CAM) for working environments. With regard to schools, adequate acoustic comfort targets are required in terms of noise control and acoustic quality. Schools must comply with the UNI 11532 for their reverberation (T), clarity (C50) and speech intelligibility (STI). In classrooms, the following values are required: T 0dB and STI>0.6. In sports facilities such as gyms or swimming pools, the requirements are T -2 dB and STI>0.5. To achieve these objectives, the insertion of acoustic treatments is often unavoidable. Acousticians commonly use the perfectly diffused theory to calculate the amount of need sound-absorbing material to comply with current legislation. The purpose of this work is to evaluate the optimal position in which to place the minimum amount of sound-absorbing treatments to reach CAM. Some university classrooms are used. These classrooms have a marble floor and plastered walls and, at 1.0 kHz, have T values between 2.5s and 4.5s, C50 between 3 dB and -0.5 dB, and ST between 0.34 and 0.47. Using an acoustic software, it was possible to estimate the minimum quantity and the optimal placement of the sound-absorbing panels to insert to reach the CAM of these classrooms.