Improving Aeroacoustic Measurements Using Optimized Microphone Cavities
C. (Colin) van Dercreek
Quantifying and identifying noise sources through experiments is a key part of reducing aeroacoustic noise generated by wind turbines, aircraft, and vehicles. Ideally, these measurements are made in open jet wind tunnels located in anechoic rooms. However, it is often more cost efficient to perform these measurements as part of an aerodynamic measurement campaign in a closed test section wind tunnel. However, closed test section wind tunnels generate significant acoustic noise from tunnel machinery, protrusions, and reflections. Additionally, the boundary layer along the tunnel wall generates hydrodynamic noise sources. Placing microphones within cavities is one approach that reduces the influence of these noise sources.
The goal of my research is to understand how the shape and materials of these cavities affects the measurement of these background sounds. By understanding the relationship between the cavity shape and the propagation of background noise within the cavity, optimized cavities can be developed. An optimal cavity improves the signal-to-noise ratio of the acoustic measurements by reducing the background noise with respect to the acoustic source being measured. These improved cavities will improvement the acoustic measurements the next generation of quieter airfoils. This work is part of the THAMES project.
VanDercreek, C.P., Majunath, P., Ragni, D. and Snellen, M., 2019. Design and Evaluation of Microphone Cavity Geometries for Wind-Tunnel Acoustic Measurements. In AIAA Scitech 2019 Forum (p. 1580). DOI: 10.2514/6.2019-1580
VanDercreek, C.P., Amiri-Simkooei, A., Snellen, M. and Ragni, D., 2019. Experimental design and stochastic modeling of hydrodynamic wave propagation within cavities for wind tunnel acoustic measurements. International Journal of Aeroacoustics, 18(8), pp.752-779. DOI: 10.1177/1475472X19889949
VanDercreek, C.P., Sijtsma, P., Snellen, M., Ragni, D., Avallone, F. and G. Simons, D., 2019. Deterministic model of acoustic wave propagation in a cavity. In 25th AIAA/CEAS Aeroacoustics Conference (p. 2425). DOI: 10.2514/6.2019-2425
Colin van Dercreek received his B.S. in Engineering Mechanics from the University of Wisconsin – Madison and his M.S. in Aerospace Engineering at the University of Maryland. He worked on experimental VTOL aircraft at the Defense Advanced Research Projects Agency (DARPA). He was heavily involved in operational testing and analysis at the Institute for Defense Analyses (IDA). His current research interests are Aeroacoustics and improving acoustic measurements in wind tunnels through optimizing the tunnel wall geometry surrounding microphones.
