Aeronautical noise suppression at transonic Mach numbers

The measurement of wind tunnel background pressure fluctuations in a Ludwig Tube is discussed. The measurements are to provide improved unsteady aerodynamic data for the design of aeronautical vehicles. The preliminary results of the facility calibration are presented. The noise generation mechanisms are discussed. The ability of conducting short duration acoustic tests is demonstrated, and amplitude and frequency data are given. Techniques of noise reduction are included.