Silencers for nitrogen, oxygen, carbon-di-oxide,hydrogen rich gases and other process gases can be supplied for both online pressure silencer as well as vent silencers. The prime requirement for a vent silencer is its ability to handle with total reliability the rapid release of large quantities of steam from high pressure to atmosphere and attenuating high levels of noise generated at the vent for steam at wide range of pressure and temperature conditions. The silencers are made out of concentric annular acoustic cylinders enclosed with a robust steel casing with dished end or flat end at one end.