Comprehensive approach for noise reduction in helicopter cabins

The work presented here settles down in the general framework of a “Comfortable Helicopter” Research program, and particularly focuses on acoustical comfort improvement in helicoptersʼ cabins. To optimize internal noise levels at given added sound-proofing weight, space and cost constraints, one needs both to have a good knowledge of noise sources and path contributions to the interior noise and to develop some efficient and innovative sound-proofing concepts adapted to the sources frequency content and localization in the helicopter. This paper presents the comprehensive approach chosen by Eurocopter including a diagnosis and modelling methodology based upon the coupling of Nearfield Acoustical Holography measurements and geometrical acoustics simulations. Innovative noise reductions concepts such as optimized sound-proofing panels and windows and Main Gear Box suspension devices have been developed. All these solutions have been tested in flight. Finally, the achieved overall performances obtained on the demonstrator are highlighted, insisting on the significant comfort improvement obtained in flight and on Eurocopter expectations for further noise reductions.