The sound absorption properties of highly porous silicon nitride ceramic foams

The sound absorption properties of highly porosity Si3N4 ceramic foams was studied and the effect of structural factors such as porosity, pore size and thickness of Si3N4 ceramic foams and the air gap backing on the sound absorption properties was systematically investigated. The results showed that the higher porosity and smaller pore size of Si3N4 ceramic foams would contribute to better sound absorption in almost entire frequency. While the thicker samples would increase the sound absorption coefficient in low frequency by shifting the sound absorption peak to lower frequency. By inserting an air gap and adjusting the pore size of Si3N4 ceramic foams, a selectively filtration of low or medium frequency could be achieved. The values of sound speed and acoustic impedance of the Si3N4 ceramic foams were notably low and decreased along with the increase of porosity.