Sound absorption characteristics of porous aluminum fabricated by spacer method

Abstract

Porous Al specimens with porosities of 85%–95% and pore sizes of 212–300to610–700μm 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.

On the compressive behavior of sintered porous coppers with low-to-medium porosities—Part II: Preparation and microstructure

“…The space holding will be removed by various ways and a pore will be left at the position of the space holder. Porosity up to 90-95% was observed [23].…”

Shape-memory NiTi foams produced by solid-state replication with NaF

“…Control of the pore volume fraction, shape and size are all accomplished by selection of the spaceholder materials which have included in previous studies; sodium chloride [29] or carbamide [30,31] for aluminum foams, polymers [32] or potassium carbonate [33] for copper foams, sodium carbonate for nickel foams [34], and ammonium bicarbonate [35] or magnesium [36] for titanium foams.…”

Sound Absorption Optimization of Graded Semi-Open Cellular Metals by Adopting the Genetic Algorithm Method

“…Highly porous cellular metals having either full-or semi-open cells have been exploited as sound absorbing materials for a range of noise and vibration control applications, particularly in hostile surroundings [1][2][3][4][5][6][7][8][9]. Compared with traditional sound absorbent materials such glass wool and polymer foams, aluminum foams are mechanically stiff, strong and stable, do not generate toxic gases in the presence of a flame, have high durability and resistance to weathering, and can shield against electromagnetic waves.…”