Sound absorption by metallic foam after triaxial hydrostatic compression

An engineering method for triaxial hydrostatic compression of metallic foam is presented to preferentially alter the foam's microstructure. The method is demonstrated on an assortment of open-cell aluminum foams with varying pore size and porosity. Measurements of acoustic absorption indicate that the compressed samples absorb significantly more sound than the conventional samples of equal thickness in the test range from 0.25 to 4 kHz. The acoustic absorption trends that result from the transformation of foam microstructure in the compressed samples are a function of the initial pore size and porosity. An analysis is presented which links the microstructure properties of compressed foam samples to conventional samples, thereby providing a means to estimate acoustic absorption trends for compressed samples through use of existing models.