ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pSA6. A technique for measuring the reflectivity of panels at low frequencies and high oblique angles.

J. J. Dlubac

R. J. Deigan

Code 721, Signatures Directorate, Carderock Div. of the Naval Surface Warfare Ctr., Bethesda, MD 20084-5000

Conventional short-pulse techniques for measuring the reflectivity of acoustic panels require that the reflected and incident waves be separated in time so that their ratio can be established. This technique is limited to moderate angles of incidence, since at high angles the direct and reflected waves overlap. An interference method is investigated as a way of making reflectivity measurements at high oblique angles. The total field (incident and reflected) near an oblique panel is measured relative to the incident field without the panel. The total field, which depends on frequency and angle of incidence as well as the panel material, is then examined and manipulated to extract information on the reflected wave. The technique is demonstrated with data reduced on steel plates.