PURPOSE: To maintain a high acoustic performance by providing a water repellent agent over the outer surface, in contact with air, of an acoustic material comprising porous ceramics.
CONSTITUTION: A water repellent agent including 0.1wt.% or more of silicone is carried by an acoustic material comprising porous ceramics having apparent specific gravity of 0.2 or more. And incoming water is repelled by the water repellent agent of the acoustic material, thereby preventing the water from penetrating into a large number of pores. Further even if the water has penetrated into the pores, the water is easily drawn out because of the water repelling property of the water repellent agent which is in contact with the water. As a result, even if acoustic performance has been lowered, it is restored in a short time.
OGUSHI ATSUSHI
TANIGAKI AKIRA
