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Acoustic absorption properties of open-cell Al alloy foams with graded pore size

By adjusting the size of preform particles and their stacking routes, the open-cell Al alloy foams with graded pore size were prepared by the melt infiltration method. The effects of pore structures and air gap on the acoustic absorption properties of open-cell Al alloy foams have been investigated. The results show that whether there is an air gap, the open-cell Al alloy foam with graded pore size exhibits better acoustic absorption properties (maximum absorption coefficient, noise reduction coefficient (NRC) and half-width of the absorption peak) than the foams with uniform pore size. The typical maximum absorption coefficient, NRC and half-width of the absorption peak are 0.96–0.99, 0.40–0.64 and 1600–3200 Hz, respectively.