"AFFDL-TM-74-139-FYA." "AD-A001 329." "Filmed 1-13-75 NTIS." Microfiche.

A computer program is presented for calculating the sound pressure level (SPL) in the jet near field which accounts for ground reflection and multiple engine operation. The prediction method is a modification of the semi-empirical technique presented in AFFDL TR-67-43 'Near Field Noise Analysis of Aircraft Propulsion Systems with emphasis on Prediction Techniques for Jets'. The modifications in addition to accounting for ground reflection allow the prediction of the SPL for the overall and three octave bands at any point in the field and require data inputs of jet exit temperature, Mach number and diameter. A brief description is presented of a noise measurement program conducted on the XB-70 aircraft during which one-third octave band noise spectra were obtained for a range of engine conditions and for various combinations of linear arrays of engines.