V. M. Kouznetsov
Central Aerohydrodynamics Inst. TsAGI), Moscow Branch, Acoust. Div., 17, Radio str., 107005, Moscow, Russia
Possibilities of complying with the community noise requirements for the supersonic civil airplane are discussed. Analysis of acoustic characteristics of the first supersonic civil airplanes Tu-144 and Concorde is given; comparison of the community noise level measurements and noise limits for subsonic passenger aircraft is carried out. Suggestions on the community noise reglamentation of SST's are considered. Possibilities of using the following ways of jet noise reduction are discussed: gas thermal shield, multilobed or corrugated nozzle, surrounding air ejection, and application of sound absorbing linings. Results of the experimental investigations of model noise-suppressing nozzle efficiency with additional surrounding air ejection through the side surfaces, of corrugated nozzles with ejectors, the interior surfaces of which are treated with sound absorbing linings, are presented. The selection method of optimum parameters of sound absorbing linings is examined. Evaluation of the possible noise level reduction of the exhaust flow at the expense of ejector noise suppressor application is carried out. It is to be emphasized that only combined application of a series of jet noise reduction methods permits one to meet the community noise requirements.