Noise comfort design approaches for next Regional Aircraft generation

摘要

The comfort inside an aircraft is influenced by several parameters, in particular the noise distribution, which typically change in amplitude and in frequency all along the passenger cabin and the cockpit. The main noise sources (power plants and the aerodynamic turbulence) are located outside of the fuselage. Looking to the noise transmission mechanism and the relevant noise controls it is enhanced the needs of efficient treatment devices able to reduce vibration and noise in the cabin. Inside the Turboprop Regional aircraft the noise comfort is dominated by low frequencies tones produced by the propeller blades annoyance; then to control their transmission the use of Dynamic Vibration Absorbers (DVA) is widely applied. ATR aircrafts family gives an example of this application in service; in fact, ATR is embodying a DVA optimized treatment, since 1987, showing comfort level competitive with similar size turbofan aircraft. Since the current Regional market forecast is for a higher passenger capacity and longer mission characteristics in compliance with the most stringent environmental limits, the airframe manufacturing are looking for a new Regional Aircraft installing higher power engines with low internal noise impact. The advanced turbo propeller engine or the new Open Rotor engine concepts, today under development, seem a more appropriate industrial answer to these market requests. Nevertheless, looking to this scenario, more effective noise treatments able to assure a comfort level equal or better than current products need to be available. This paper addresses these last issues and reports some industrial research results coming from preliminary analysis of candidate new treatments for tonal noise reduction. They take into account the long time Alenia experience on ATR products and the exploitation of new concepts developed within relevant EU research programmes MESA, MESEMA, FACE, CREDO, performed with a significant contribution by all authors. The outcomes of such studies provide also a synthesis of open items needed to be further analysed in order to meet the comfort requests of the future Regional market, trying to satisfy, both the final customer (the passenger) then the industry and the operators of the market.