Helicopter noise in urban flight

Abstract

The present paper deals with a test campaign carried out in order to investigate the interaction between sound waves emitted by an helicopter and a model of an idealized urban contest. Test campaign was performed in Politecnico di Milano anechoic room, in order to analyze data produced by only helicopter noise. Set up consisted in a two blade main rotor helicopter model and a rectangular prism in aluminium as the landing building model. Ground observers perception was recorded by means of a surface microphone and a realistic landing trajectory was approximated as a succession of fixed point measurements. Collected data have been analyzed through acoustic spectra and sound maps. Spectra were used to comprehend physical phenomena, such as reflection, diffraction and shielding, and to analyze the different components of helicopter noise. Sound maps analysis enabled to get a global perspective of involved phenomena and to understand how much people close to building are stressed by an helicopter approaching an elevated urban helipad.