Amargianitakis, DC, Self, RH, Torija Martinez, AJ 
ORCID: https://orcid.org/0000-0002-5915-3736 and Synodinos, AP
2019,
Influence of sound reflection on aircraft directivity and
lateral attenuation on the ground
, in: Internoise 2019, Noise Control for a Better Environment, 16/06/2019 - 19/06/2019, Madrid, Spain.
Abstract
The calculation of the lateral attenuation correction for computing aircraft noise
footprints on the ground, as proposed by Doc29 and AIR5662, is based on
semiempirical methods not suitable for accounting for the particular
characteristics of some of the novel aircraft designs under study; involving new
configurations and propulsion and power systems. The lateral attenuation
correction is known to depend on three factors: engine installation e_ects,
ground absorption, and refraction and scattering of the sound. This study aims
to numerically calculate the e_ects of the sound produced by the aircraft main
sources (fan, jet) when reflected and scattered o_ of the wing, tail-plane
surfaces and the fuselage of the aircraft. A simple 3D model geometry was
used, approximating that of an A320, a MD11 and a MD83. Subsequently
modelling the main sound sources as acoustic monopoles and using ray theory,
a sound directivity field around the aircraft was calculated, which in turn was
propagated to the ground. Then employing typical constant altitude flyovers, the
Sound Exposure Level (SEL) were calculated and compared to an equivalent
spherically symmetric source. It is shown that aircraft directivity is highly
dependant on the nature of noise sources, their position relative to reflective
surfaces and the geometry of those surfaces.
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