Description: Closed wind tunnel beamforming for aeroacoustics has become more and more prevalent in recent years. Still, there are major drawbacks as current microphone arrays are rather larger and hard to install and conventional beamforming and deconvolution techniques do not work well in low signal-to-noise environments. Outlined in the proposal is a phased airfoil imaging microphone array located inside the wind tunnel which utilizes Functional Beamforming, a modification of conventional beamforming. A completed unit would be comprised of several airfoils with microphones placed in a linear fashion along the leading edges. Functional Beamforming is a breakthrough algorithm that will allow for much better beamform mapping with much smaller arrays than what is currently available. Because of the potential small size of the array, it would be easy to install and implement. Placing the array in the tunnel also allows for numerous viewing angles of the test models as opposed to a single view provided by wall arrays. Phase I will focus on designing, building, and testing the multi-arm airfoil array to troubleshoot operation and eliminate showstoppers. Functional Beamforming software is currently available and does not require further development the rights of which are owned by OptiNav, inc. The PI has a plethora of experience and knowledge in acoustical testing and phased imaging arrays and was a key investigator in early closed wind tunnel acoustical testing. The proposal outlines a work plan which includes testing in the Kirsten Wind Tunnel at the University of Washington which has already agreed to support the tests.

Benefits: The innovation would primarily appeal to NASA owned closed wind tunnels like ATP facilities including the 9x15 foot Low Speed Wind Tunnel at GRC, the 14x22 foot Subsonic Tunnel, and the National Transonic Facility at LaRC.

The innovation would also appeal to all other government, university, and private closed wind tunnel facilities around the world. Open wind tunnels would also be another application although not the primary target. Basically, any wind tunnel facility with an interest in testing acoustics would be a potential customer. Functional Beamforming has an even greater number of applications. The software can extend too many other fields including underwater acoustics, cellular telephone networks, radio astronomy, seismology, medical imaging, and any other field that relies on conventional beamforming.