Windows sound insulation: experimental evaluation of different traffic noise spectra

The influence of the traffic characteristics on the indoor noise transmitted by windows is evaluated by means of laboratory measurements into coupled reverberating rooms; different traffic noise spectra are registered and reproduced into the emission room, simulating the outdoor conditions; different windows are installed on the wall between the rooms and the noise spectra into the receiving room, simulating the indoor conditions, are measured and a frequency analysis is carried out. Comparing data obtained by the spectrum proposed by ISO 140 - 3 and the reproduced spectra showed no influence on the Rw value; nevertheless, considering the Ctr corrections such as in UNI EN ISO 717 – 1, significant differences were found. The A weighted levels abatements between emission and receiving room show higher values of Le – Lr for the High Speed Trian spectrum, which is the one with the lower levels at low frequencies; all windows, in fact, have worst acoustics performances at low frequencies.