Simulation of jet-noise excitation in an acoustic progressive wave tube facility

Acoustic excitation produced by jet-engine effluxes was simulated in a prog ressive wave tube (APWT) facility with a computer-based control system. The APWT siren is driven by a signal generated numerically in a PC and then co nverted into analog farm. Characteristics of the acoustic pressure measured by a microphone are analyzed in digital form and compared with those presc ribed for simulation. Divergence is compensated by immediate modification o f the driving signal and this action is repeated in the form of iterative p rocess until the test specification is attained. Typical power spectral den sity (PSD) shapes with maxima at low and high frequencies were simulated. A "tailoring" approach has been also achieved when a test specification was determined directly from field measurements for the particular aircraft und er consideration. Since acoustic pressure signals of high level differ fi-o m the Gaussian random process model, particularly in terms of asymmetric pr obability density function, a method has been developed to make the driving signal also non-Gaussian by simulating skewness and kurtosis parameters of the APWT acoustic excitation simultaneously with PSD control. Experimental results with Gaussian and non-Gaussian characteristics obtained for variou s PSD specifications including sharp and narrow peaks are presented in the paper. (C) 2001 Acoustical Society of America.