Acoustic Treatments Aiming to Achieve the Italian Minimum Environmental Criteria (CAM) Standards in Large Reverberant Classrooms

Abstract

A recent Italian legislation has established the Minimum Environmental Criteria (CAM) for any working environment. In regards to schools, adequate acoustic comfort targets are required in terms of noise control and acoustic quality. Schools must comply with the Italian technical standard UNI 11532 for their reverberation time (T), clarity (C50) and speech intelligibility (STI). In classrooms, the following values are required: T<0.7s, C50>0dB, and STI>0.6. In sports facilities such as gyms, the CAM requirements are T<1.5 s, C50> -2 dB, and STI> 0.5. To achieve these objectives, the insertion of acoustic treatments is often unavoidable. The new requests for classrooms are leading acousticians to propose sound correcting interventions in many educational buildings. Acousticians typically use the perfectly diffused theory to calculate the minimum amount of needed 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 the CAM in some university classrooms. These classrooms have a marble floor and plastered walls and, at 1.0 kHz, have T values between 2.5 s and 4.5 s, C50 between 3 dB and -0.5 dB, and STI 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 in each classroom to reach the CAM.