Muffler Systems for Aircraft Noise Reduction

Abstract

Noise reduction is considered to be one of the major challenges in aircraft industry, since beginning of bi-plane era to recent advanced fast jet aircraft era. In general, aircraft noise can be classified into two categories i.e. aircraft interior (cabin noise) and exterior noise. Some of the typical structure borne and air borne noise sources for both interior and exterior noise are engine, cabin conditioning system, fuselage, landing gear, canopy and wings etc. Over the years, the structure borne noise has been effectively reduced by means of active and passive control of aircraft structures. The airborne noise source is aerodynamic in nature and has broad band frequency content. This can be effectively reduced by preventing the formation of turbulence or wake. For the past few decades mufflers have been used in aircraft industry to reduce the noise generated by propulsion system and cabin conditioning system. This paper gives an overview of noise in aircraft, the application of mufflers used in the general aircraft industry and also how effectively the muffler systems can be designed by taking into account the source and termination conditions.