Acoustic wave propagation through the shear layer of the DNW large open jet wind tunnel

The adequacy of the sound refraction theory corrections to measurements of the aeroacoustic signals obtained from models immersed in a jet shear in the German-Dutch wind tunnel were evaluated. Four air horns and a speaker served as an aerodynamically shaped model for the calibrated noise source. The test channel is surrounded by an anechoic chamber to eliminate random noise. Data were taken with microphones traversing the flow, out of the flow, and in a stationary position. The Amiet shear layer corrections were determined to be valid in most applications. However, with the presence of both high frequency and high Mach number, the refraction angle correction must be used to account for additional shear layer effects on the sound pressure level