Underwater sound absorption property of porous aluminum

Porous aluminum was prepared by negative pressure infiltration process using removable granules. Underwater sound absorption coefficient α of the porous aluminum was determined by a pulse tube method. The relationship between α and pore structure of porous aluminum was studied. α increases remarkably with the decrease of pore diameter from 5 to 2 mm. It shows that there is an optimal porosity (75–80%) with which porous aluminum gives the best sound absorption. α increases with the sampleʹs thickness L. The thin sample doesnʹt absorb sound (such as L=15 mm).