Acoustic Absorption of a New Class of Alumina Foams with Various High-Porosity Levels

Recently, a new class of ceramic foams with porosity levels up to 90% has been developed as a result
of the association of the gelcasting process and aeration of the ceramic suspension. This paper presents
and discusses original results advertising sound absorbing capabilities of such foams. The authors man-
ufactured three types of alumina foams in order to investigate three porosity levels, namely: 72, 88, and
90%. The microstructure of foams was examined and typical dimensions and average sizes of cells (pores)
and cell-linking windows were found for each porosity case. Then, the acoustic absorption coefficient was
measured in a wide frequency range for several samples of various thickness cut out from the foams.
The results were discussed and compared with the acoustic absorption of typical polyurethane foams
proving that the alumina foams with high porosity of 88–90% have excellent sound absorbing properties
competitive with the quality of sound absorbing PU foams of higher porosity.