Aircraft and Airport Transportation Noise Sources and Control

The number of aircraft used for civilian and military air transportation has increased steadily during the last decades. Not only were the jet engines noisier than corresponding piston engines on airliners, since they were more powerful, but the noise was more disturbing because it had a higher frequency content than piston engines. Methods for reducing jet engine noise include modifying the unsteady flow field, redirecting the sound generated, absorbing the sound using acoustical treatments, and/or combinations of all three. Aircraft propeller and helicopter rotors are major noise sources that are difficult to control. Active control of the structure close to the engine can be undertaken to reduce structure-borne noise reaching the passenger cabin. Approaches to mitigate perceived noise problems associated with civil aircraft operations in airports include specific noise control approaches to reduce noise at the source and specific airport noise control measures.