KTH background noise silencer is suitable for installation in the air-conditioning duct work or construction or technological opening where noise reduction is required. The noise silencers are absorption-based or resonance-based. The design of the noise silencer’s structure is developed so that characteristic noise of the noise silencer and pressure loss are significantly eliminated. Achieving of lower pressure loss results in reduction of required external pressure of the system, and hence power input of the device motor. The background noise silencers comprise zinc-coated metal sheet with aerodynamic lead-ins on both sides and with absorption material and backed fabric inside the silencers. The silencers may be available in sanitary version or from stainless-steel upon request. A wide dimensional series of the noise silencers allow installation into almost any duct work cross-section. The manufacturer recommends that composition of equal lengths of the noise silencers are always used.