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SAE AIR1906 Revision A, August 1, 2012
Estimation of One-Third-Octave-Band Lateral Attenuation of Sound from
Jet-Propelled Airplanes
Description / Abstract:
BACKGROUND: The determination of noise levels on the
ground resulting from an airplane in flight is important for the
estimation of noise levels around airports for land-use planning
purposes and other application. A significant component in the
prediction of ground noise levels is the estimation of the
attenuation of sound as it propagates from an airplane to locations
on, or near, the ground plane. This sound attenuation depends on
atmospheric absorption, sound wave divergence, effects associated
with the ground, meteorological conditions, and details of the
installation of the engines on an airplane. The principal effects
of the ground are those associated with the interference of the
direct and reflected sound waves (see section 3). For propagation
to the side of the flight path, the sound attenuation caused by
factors which are not readily accounted for are referred to as
lateral attenuation in this document. Factors that are embodied in
the lateral attenuation with surface undulation); meteorological
effects such as wind and temperature gradients; and engine
shielding and/or installation effects.
The Society of Automotive Engineers' A-21 Committee on Aircraft Noise undertook the development of a uniform and consistent method for the prediction of the attenuation of noise propagating from an airplane to locations near the ground to the side of the flight path. The first phase of attenuation in frequency-weighted and time-integrated measures of noise. That prediction procedure is contained in AIR 1751 (Reference 1)*. The prediction procedure in this AIR 1906 is a contribution toward the second phase of the project in which the attenuation of airplane noise, propagating toward a lateral ground location, is considered for individual one-third-octave-band sound pressure levels in a free-field environment (the data in AIR 1751 are not fee-field) and as a function of sound-radiation angle (or time). Sources of the data used for the analyses to obtain values of lateral attenuation, which were subsequently used in the development of the prediction procedure, are given in section 6. The need to include the dependence on sound-radiation angle (or time) requires a definition of lateral attenuation which is different from that in Reference 1 for time-integrated noise descriptors.
The Society of Automotive Engineers' A-21 Committee on Aircraft Noise undertook the development of a uniform and consistent method for the prediction of the attenuation of noise propagating from an airplane to locations near the ground to the side of the flight path. The first phase of attenuation in frequency-weighted and time-integrated measures of noise. That prediction procedure is contained in AIR 1751 (Reference 1)*. The prediction procedure in this AIR 1906 is a contribution toward the second phase of the project in which the attenuation of airplane noise, propagating toward a lateral ground location, is considered for individual one-third-octave-band sound pressure levels in a free-field environment (the data in AIR 1751 are not fee-field) and as a function of sound-radiation angle (or time). Sources of the data used for the analyses to obtain values of lateral attenuation, which were subsequently used in the development of the prediction procedure, are given in section 6. The need to include the dependence on sound-radiation angle (or time) requires a definition of lateral attenuation which is different from that in Reference 1 for time-integrated noise descriptors.
SAE AIR1906 Revision A, August 1, 2012
Estimation of One-Third-Octave-Band Lateral Attenuation of Sound from
Jet-Propelled Airplanes