Noise Control of Aircraft Auxiliary Power Units 670548
Lower noise levels are required from auxiliary power unit (APU) installations onboard commercial aircraft to make these compact, high-energy, turbine power sources more acceptable at terminal gate positions. Special acoustical materials and installation techniques that fulfill high-temperature requirements and stringent fire-safety demands are needed to control the three principal noise sources: the inlet, the case, and the exhaust. In addition, practicable noise criteria are needed which do not create requirements that excessively compromise APU performance or increase installed weight. Fulfillment of the preceding requisites for APU installations on the Boeing 727-100 and 737 aircraft is discussed. Suggestions for noise control practices to be followed in turbine design are also presented.