Noise reduction studies of several aircraft to reduce their aural detection distances

A study was conducted to assess the extent to which practicable reductions of the external noise level of various aircraft could be achieved by different methods. The aircraft included in the study are the O-1, O-2, U-10, OV-1, and A-6. The noise signatures obtained from field measurements and the estimated aural detection distance of aircraft operating in low speed cruising flight are presented. The characteristics of each aircraft and the modifications made to reduce the aerodynamic noise are explained. Tables of data are included to show the effectiveness of the noise reduction modifications for each aircraft.