Dipole Modeling and Nondimensionalization of Airframe Noise

Abstract

Airframe noise measurements may be correlated and made more physically meaningful by a conversion from a decibel or dimensional form to a coefficient or nondimensional form, in particular for radiation in a single direction, chosen to be directly below the aircraft. For radiation in other directions, a three-dipole model may be used, and three additional coefficients defined. Examples of the coefficients are given for various flight and configuration conditions for both the DC-9-31 and the DC-10-10 aircraft. A significant body of airframe noise data has been published and is available for conversion to nondimensional form, both for the representation of overall sound pressure levels and for any one or more one-third octave band levels.