Regarding ventilation silencers in buildings and for industrial applications at room temperature, they usually consist of an outer casing (mostly made of non-stainless steel, most of the time: galvanized) and of an absorbing filling (quite often: mineral wool) covered by a surfacing (mostly: a fiber glass) and also by a perforated protection (mostly: made of galvanized steel). For the outer casing, if required: a powder coating usually provides the best possible protection against corrosion: classification up to C5 according to ISO 12944.

As far as simple dissipation silencers are concerned, they are soundproofing equipment belonging to the category of dissipative silencers for which the sound absorption material is placed exclusively on the inside of the outer envelope. In most cases, such silencers are round and are intended to be inserted in networks with ducts being themselves of circular cross section (silencers with rectangular cross section, possibly square can be envisaged in some cases and are intended to be inserted into networks of ducts being themselves of rectangular or enventually square cross section). The acoustic performance of such silencers (insertion loss) is highly dependent on the considered frequency and is linked to the fluid velocity, to the acoustic thickness of the lining, its nature (in particular: the flow resistance of the filling and of its covers if any), to the free inner dimension for the passage of fluid, and also to the length of the silencer. Such silencers are characterized by a total pressure loss (also called pressure drop) being low because exclusively dependent on the roughness of the walls and on the length of the silencer (usually negligible if the flow velocity of the fluid is low enough).

Regarding splitter silencers (also called baffle silencers), they are soundproofing equipment belonging to the category of dissipative silencers for which the sound absorption material is held in frames (usually metallic: in non-stainless steel) forming splitters between which the fluid flows. Most of the time, such silencers have a rectangular cross section and are intended to be inserted into networks of ducts being themselves of rectangular cross-section (silencers with circular cross-section, with circular central splitter and, where appropriate with one or more ring-shaped intermediate splitters can be envisaged in some cases and are intended to be inserted into networks of ducts being themselves of circular cross-section). The acoustic performance of such silencers (insertion loss) is very dependent on the considered frequency and is related to the fluid velocity, to the thickness of the splitters (baffles), to their nature (including: fow resistance of the filling and of its cover if any), to their spacing, as well as to the length of the silencer. Such silencers generate a total pressure loss (also known as pressure drop) mainly related to the thickness of the splitters, to their spacing, and also to their geometry (profiling of upstream and downstream extremities if any) as well as to the length of the silencer.

In some cases, the metallic parts of dissipative silencers for industrial applications at room temperature can be made of stainless steel (SS 304, SS 316, SS 321) or even replaced by plastic parts in extreme cases where the transported fluid is extremely corrosive (silencers for smoke ducts at low temperature for example).

As required, the absorbing filling may consist of acoustic foam or of polyester wool and and may for some applications be protected by a waterproof surfacing (polyurethane film and for extreme cases: painting).

The prediction of acoustic and aerodynamic performance of dissipative silencers such as ventilation silencers in buildings and for industrial applications at room temperature can be performed with the simulation software SILDIS®®.