Correlation between the shape of substitution ducts and insertion loss of silencers

Silencers are typical devices used for the reduction of noise in ventilation systems, which can be found in almost all industrial, service or residential installations. Determination of acoustic parameters for specific HVAC devices, like silencers, is within the scope of specialised laboratories. With the silencers, two main parameters should be taken care of: the first one is sound attenuation and the second one is pressure losses. In the presented paper, the focus is on measurement methods described by standard ISO 7235:2009. This standard specifies the methods for determining the sound power level of the flow noise generated by silencers, the total pressure of silencers and the insertion loss of silencers with and without airflow by using the substitute object. In this work, we focused on the correlation between the shape of the substitution duct and its acoustic parameters and its relation to this with the final result of insertion loss of a silencer.