Materiales de Construcción, Vol 58, No 291 (2008)

Acoustic properties of aluminium foams


https://doi.org/10.3989/mc.2008.v58.i291.109

M. A. Navacerrada
Grupo de Investigación en Acústica Arquitectónica, ETS de Arquitectura, Universidad Politécnica de Madrid, Spain

C. Díaz
Grupo de Investigación en Acústica Arquitectónica, ETS de Arquitectura, Universidad Politécnica de Madrid, Spain

A. Pedrero
Grupo de Investigación en Acústica Arquitectónica, ETS de Arquitectura, Universidad Politécnica de Madrid, Spain

L. E. García
Departamento de Ingeniería de Materiales, ETS de Ingenieros de Minas, Universidad Politécnica de Madrid, Spain

Abstract


The article discusses normal incidence sound absorption by aluminium foam manufactured with powder metallurgy technology. Aluminium foams with different surface morphologies were obtained by varying the type of precursor and adding filler materials during the foaming process. The sound absorption coefficients found for these aluminium foams were compared to the coefficient for commercial foams marketed under the name ALPORAS. The effect of foam thickness on the absorption coefficient was studied for each sample prepared.

The combination of good acoustic and mechanical properties makes aluminium foams particularly attractive products. The study included an analysis of the effect of 2-, 5- and 10-cm air gaps on the sound absorption coefficient. The results showed that such gaps, which are routinely used in construction to reduce the reverberation period in indoor premises, raised the low frequency absorption coefficient significantly. This increase was found to depend on aluminium foam density and thickness and the depth of the air gap. In this same line, we have investigated the absorption coefficient of the aluminium foams combined with a mineral fiber panel.

Keywords


sound absorbers; absorption coefficient; impedance tube

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