The sound absorption performance of the highly porous silica ceramics prepared using freeze casting method.

Highly porous silica ceramics with unidirectional pores were prepared using the freeze casting method. By adjusting the solid content and freezing temperature, the porosity of the ceramics was tailored in the range of 78.20%‐84.59% and pore size in the range of 8.4‐71.4 μm, respectively. Sound absorption properties of porous silica ceramics was studied and the effect of structural factors was systematically investigated. The results showed that higher porosity and smaller pores of the porous ceramics favored the sound absorption in the entire sound wave frequency. By backing the sample with small pore size porous ceramics, the sound absorption property was enhanced, particularly in the low and medium frequency range, thus the sound absorption peak shifted towards lower frequency. The presence of air gap in the back would also favor sound absorption in low and medium frequency range. The as‐fabricated porous silica ceramics owed excellent sound absorption properties due to their unidirectional pores and low flow resistances. [ABSTRACT FROM AUTHOR]