Abstract: A thermal shock resistant porous sound absorbing body having high durability in which the prior drawbacks of sound absorbing bodies have been obviated, is produced by sintering a mixture comprising 100 parts by volume of ceramic particles having a bulk density of 1.2-2.0 kg/l, a grain size of 0.3-4.0 mm, a thermal expansion coefficient of less than 70.times.10.sup.-7 /.degree. C. and a fire resistant temperature of higher than 1,000.degree. C. and 4-18 parts by volume of an inorganic binder having a melting temperature of lower than that of the ceramic particles and a thermal expansion coefficient of lower than that of the ceramic particles, and further a sizing agent.

Abstract: The disclosed silencer has noise-absorbing partitions disposed in a gas duct in parallel with but with a spacing from outer walls of the duct, so as to define gas passage means and noise-absorbing space means in the duct. The noise-absorbing space means is closed by noise-shielding plates at inlet and outlet ends of the duct. A plurality of gas chambers aligned along the line of gas flow through the duct are formed in said noise-absorbing space means by disposing noise-shielding sectional walls therein.

Abstract: The invention relates to an improvement of a silencer arranged in a gas flow passage of a gas supply or exhaust system and includes a sound absorbing material lined on wall surfaces of the gas flow passage in a duct casing. According to the invention, the sound absorbing material is covered with guard plates, each provided with a number of sound absorbing apertures and oblique plates located at edges of the apertures, for preventing gas flow from entering the sound absorbing material. The silencer according to the invention is capable of preventing accumulation of dust on the sound absorbing material and eliminating damage to the sound absorbing material due to entering of the gas flow thereinto. Thus, the silencer is particularly useful to diminish noise which is caused by gas flow when the gas contains a great amount of dust or when the gas flows at a high speed.