Improved prediction of community noise footprints from high performance military aircraft.

Abstract

Experimental research has shown how the addition of properly designed chevrons to model scale supersonic nozzles reduces the noise of the high speed jets issuing from such nozzles. It has also been shown that, to reasonable accuracy, this noise benefit scales between small‐ and moderate‐scale nozzle geometries. The new advanced acoustic model (AAM) developed by Wyle Laboratories has the capability to use noise source data to produce dynamic acoustic footprints showing noise exposure in the vicinity of airfields: especially for landing and take‐off operations. AAM uses information on aircraft engine jet exhaust noise sources for specific aircraft engine operating parameters and given flight conditions. This presentation describes the measurement and modeling of jet noise reduction using chevrons in both small and moderate scale nozzles. Then the AAM is used to demonstrate the expected change in acoustic footprint size for a full‐scale jet aircraft, where it equipped with chevrons. The effects of the chevrons are described as a decibel correction to the noise source spheres used by the model. The AAM is run for a simulated trajectory of a typical operation for a jet aircraft with and without chevrons to show the effects on the acoustic footprint.