EXAMINATION OF ACOUSTIC ABSORPTION CHARACTERISTICS OF FOAMED ALUMINUM

It has been investigated that the influence of structural parameters o f foamed aluminum (FA) is important for its acoustic absorption charac teristics. Unlike other fibrous sound-absorbing materials, the relatio n of acoustic absorption coefficient of FA to the porosity is uncertai n. The effect of pore size is non-monotonous, and higher absorption ca n be obtained only in moderate pore sizes, which is clearly connected with the flow resistance. Absorption at frequencies lower than 800 Hz can be improved by an air gap layer between the sample and the rigid w all. It is also found that compressive deformation is an effective mea sure to increase the peak absorption and widen the frequency range of higher absorption.