Print Email Facebook Twitter Sound adsorption tests on polyurethane and liquid soap foams for anechoic enclosures Title Sound adsorption tests on polyurethane and liquid soap foams for anechoic enclosures Author Krishnappa, G. Levy, G.G. Macaulay, G.A. Institution National Research Council Canada, Division of Mechanical Engineering, Engine Laboratory Date 1969-02-28 Abstract An investigation was made of the normal and random incidence absorption of samples of 2-in thick polyurethane foam selected for use in the construction of an anechoic enclosure for lifting-fan noise studies. Impedance tube measurements gave normal incidence absorption coefficients ranging from 0.38 at 500 c/s to 0.91 at 1500 c/s. Reverberation time measurements carried out at the NAE Acoustic Test Facility indicated a random incidence absorption coefficient of 0.79 at 500 c/s, increasing to almost 1.0 at 1250 c/s, after correction for diffraction effects. Reverberation time measurements on 1-in, 2-in, and 4-in thick liquid soap foam showed high sound absorption. A4-in thick foam gave a random incidence coefficient of 0.72 at 300 c/s to 1.0 at 800 c/s (not corrected for the effects of diffraction). To reference this document use: http://resolver.tudelft.nl/uuid:afb9dd44-f573-4b38-a62f-95a41e35ad0a Publisher National Research Council Canada Access restriction Campus only Source National Research Council Test Report MET 499; NRC No. 10687 Part of collection Aerospace Engineering Reports Document type report Rights (c) 1969 National Research Council Canada Files PDF MET-499.pdf 2.92 MB Close viewer /islandora/object/uuid:afb9dd44-f573-4b38-a62f-95a41e35ad0a/datastream/OBJ/view