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Procedures for measurement and evaluation of aircraft noise are contained in FAR Part 36 which was formulated in the late sixties. Over six years experience with this regulation has resulted in more than 5000 noise certification actions on the Boeing family of commercial jet transports. This experience has identified several potential areas for improvement of the regulation. Recommendations are presented for modifications to those portions dealing with noise demonstration procedures and test limitations. It is believed these modifications will make complying with the regulation less complex, while improving the technical validity of measured noise levels.

Recent developments in sonic inlet technology are presented with particular emphasis on STOL propulsion systems. Inlet noise reduction requirements are discussed for an augmentor wing and an upper surface blowing type of propulsion system. The current state of the art is discussed with respect to performance and noise potential of different sonic inlet concepts. Acoustic and aerodynamic performance comparison is presented for several inlet configurations based on experimental results.