Sound absorption characteristics of porous aluminum fabricated by spacer method

Porous Al specimens with porosities of 85%-95% and pore sizes of 212 - 300 to 610 - 700 μ m were fabricated by the spacer method, and their sound absorption coefficients were investigated by the transfer function method. The sound absorption coefficient increased with porosity. However, there was no apparent correlation between pore size and sound absorption coefficient. Also, the sound absorption coefficient depended on the thickness. The sound absorption coefficient of a specimen was significantly improved by the modification of aperture size, even if the porosity and pore size were unchanged. Therefore, it is suggested that sound absorption behavior is strongly affected by not only the porosity and pore size but also the aperture size for porous Al fabricated by the spacer method.