To compare two different constructions of noise silencers is the aim of this paper. All buildings used for intensive animal production (poultry, pigs, rabbits breeding) are equipped by forced ventilation or air-conditioning. Food industry and wood processing industry need also intensive ventilation or air-conditioning to provide a suitable and comfortable indoor environment either for the people or for the technological processes. Principle parts of ventilation system like fans, or air streams passing through air ducts, distribution elements and others components are the main source of noise. The most common air ducts are of round profile. The noise level can be reduced by use of silencers. The noise control can be based on information provided by manufacturer of fans and on theoretical estimation including the calculation of aerodynamic noise generated by airflow through the air ducts and other air distribution components. Cylindrical silencers are usually used as a part of ventilation equipment in conjunction with axial fans or installed together with round duct system. There are three main factors which are expected from the noise silencers: noise reduction, low hydraulic resistance a minimal dimensions. These parameters were used as criteria for tested silencers evaluation. In the case of direct installation near to the fan the special Spiral silencer has better results of noise reduction than the standard cylindrical silencer MAA. The other advantage is also minimal dimensions and easy installation into the air-duct. The high hydraulic resistance is the main disadvantage of tested Spiral silencer.
