Acoustic fatigue is due to a very high intensity excitation as a result of pressure waves caused by either engine or aerodynamic effects. Acoustically-induced cracking has occurred on the external surface of the lower nacelle and aft fuselage skins on the F/A-18, as illustrated in Figure . In the former region, overall sound pressure levels greater than 170dB have been measured in flight [l]. These high sound pressure levels appear to be a result of an aerodynamic disturbance at the inlet lip
