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BEFORE an evaluation of suppressors can be made or before a sensible discussion of suppression goals can be carried on, terms, conditions, and possibilities must be understood. A five-number system for evaluating suppressors is proposed. Methods of jet noise suppression undergoing general development today include frequency shifting, jet spreading, and jet velocity reduction. Basic types of jet spreaders and velocity reducers are shown and ratings given. Combinations of types have resulted in increased suppression in many instances.

Because of the rapid growth of air travel, both cargo and passenger, the payload capacity required for future transport aircraft is too great to be accommodated by fuselages of conventional configuration (that is, single-deck, single-aisle, up to 6 seats abreast). Fuselage design philosophy was therefore re-evaluated in a recent Douglas study, and this paper reviews some of the features of that study. Factors affecting fuselage design are outlined and trends are discussed. It is concluded that the forthcoming wide, single-deck fuselage, seating up to 10 abreast, will have a potential capacity of about 550 passengers. For larger capacities, the greater efficiency of multi-deck fuselages over that of the single-deck becomes increasingly apparent on a per-passenger basis. The use of multi-deck fuselages, however, will raise new problems-particularly those of airport terminal design and passenger evacuation-but these should not prove insurmountable.

SAE Committee A-21, Aircraft Exterior Noise Measurements, was formed in 1961 to develop recommended practices for use in the evaluation of aircraft noise as it relates to airport neighborhood annoyance problems. The general areas of interest to the committee include the measurement, propagation, prediction and subjective rating of aircraft noise. This paper discusses the evaluation of aircraft neighborhood noise levels and describes the subjective measures by which comparisons can be made. Included in the discussion are the recommended practices adopted by SAE and those that are being studied by Committee A-21.