Propagation of noise generated by light-lift helicopters in natural environments: a case study in the Italian Alps

The use of light-lift helicopters in the Italians Alps has received some attention in the recent years as an alternative to cable extraction in the case of long extraction distances coupled with terrain obstacles. By contrast helicopter logging rises discussion about environmental noise propagation especially when logging is performed in proximity of Sites of Community Importance (SCIs) or Special Areas of Conservation (SACs). As a consequence, the purpose of this study is to evaluate the potential area of influence of light-lift helicopter logging by performing a noise propagation analysis. The noise measurements consisted in monitoring the noise level according to the position of the helicopter and as a consequence also to the different work elements of the helicopter logging. In order to collect information about the position of the helicopter respect to the sound level meter, a time study supported by GNSS receiver mounted inside the helicopter was thus performed. Noise propagation analysis uses GIS a tool specifically developed by Colorado State University able to calculate noise propagation patterns for one-third octave frequency bands (0.125-2 kHz) around a point sound source