| 摘要 |
1457789 Silencing jet propulsion plant SOC NATIONALE D'ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION 2 Aug 1974 [31 Aug 1973] 34200/74 Heading FIJ The noise of an aircraft jet nozzle I perceived by an observer at A is reduced by mounting a further quieter jet nozzle 2 between the jet nozzle 1 and the observer. Several quieter jet nozzles 2 may be provided, each arranged in a direction in which it is desired to attenuate the noise of jet nozzle 1. Each jet nozzle 2 may have a silencing notch 4, as disclosed in Specification 1453990 disposed in the desired direction of attenuation, or may be silenced in other ways, e.g by hinged panels as disclosed in Specifications 1457790 and 1364007. Each jet nozzle 2 may have a noise level about 15 PNdB less than that of jet nozzle 1.
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