Gas Turbine Auxiliary Power Unit Noise and Its Attenuation

The advent of the on-board gas turbine auxiliary power unit in commercial aircraft created problems of excessive noise levels affecting both passengers and aircraft personnel. This paper analyzes those problems and outlines the advanced techniques being used to reduce gas turbine noises to an acceptable level. Being directed primarily at the gas turbine engineer, a brief explanation of pertinent acoustical terminology is presented to provide a basis for his understanding. Treatment of the major noise sources of a gas turbine and its installation are discussed and evaluated from the standpoint of maximum noise reduction.