Abstract:

ESDU 87011 provides a computerized method for the prediction of pure jet noise levels in flight from a static jet noise database. The procedure considers one-third octave band levels and is applicable to single-stream circular nozzles. Given a static jet noise database (either measured or predicted) at a number of angles for a certain set of jet operating conditions, it is possible to estimate jet noise spectra for various flight angles to, and distances from, the observer. No account of atmospheric attenuation is included. The method works by computing first the spectral shape change which arises from changes in the jet refraction due to flight conditions. Noise spectra are subsequently adjusted in both amplitude and frequency using empirically derived correlations. Spectrum levels in one-third octave bands are computed and output in the frequency range covered by the static jet noise data.

Two computer programs, known as ESDUpacs A8711 and B8711 accompany this item.