Aluminum foams with spherical cells were produced by a pressure infiltration process, and their sound absorption behaviors were examined and correlated with the air flow resistance. It is shown that the small apertures or pore openings on the cell walls play an important role in determining the sound absorption behavior of the foams due to the significant influence on the air flow resistance of the foams. The foams with the same porosity and pore opening size but different pore sizes have similar air flow resistance and sound absorbing performance, suggesting that there is no necessary relationship between the pore size and sound absorption performance of the present aluminum foams. With decreasing the pore opening size, the air flow resistance increased and the low-frequency absorption peak shifted towards lower frequencies but the height decreased. When the two samples with different pore sizes were put together, the sound absorption behavior of the combined samples was dependent on the pore size of sample facing the sound waves. Relatively large pores in the face side lead to relatively high low-frequency absorption peak.
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