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Assessment of Operational Progress of NASA Langley Developed Windshield and Microphone for Infrasound
Final rept. Nov 2011-Jan 2013
ARMY RESEARCH LAB ADELPHI MD
Pagination or Media Count:
A recent National Aeronautics and Space Administration NASA effort to create a compact alternative to porous hose windscreens for infrasound applications resulted in the creation of spherical, closed-cell polyurethane foam windshields. Some researchers suggest that closed-cell foam windshields, at infrasound frequencies, sound should pass through the material of the foam to reach the enclosed microphone. This report details an U.S. Army Research Laboratory attempt to independently observe the experimental results reported in the literature and to evaluate compact, non-porous, spherical windshields for use in Department of Defense infrasound applications. Transfer functions between an instrument grade microphone and an infrasound microphone covered by eight different densities and thicknesses of spherical closed-cell foam windshields demonstrate at least a 30 dB decrease in sound level at the interior microphone across all of the frequencies studied regardless of foam density or thickness.
APPROVED FOR PUBLIC RELEASE