Acoustical Rating and Classification of Ducted Silencers: A Pilot Study. Nordtest Project 877-90.

摘要

Single number rating of ducted silencers is studied. It is assumed that the best rating is obtained by looking at the reduction in A-weight sound pressure level in the room to be ventilated. Typical system configurations are looked upon and calculations based on acoustical data of fans, bends, ducts, silencers, dampers and air terminal devices are carried out. The results indicate that the attenuation of a silencer will vary from one configuration to another and from one position in the duct system to another. However, the results also indicate that the rank order between different silencers will not vary as much from one system configuration to another. As fan generated and damper generated aerodynamical noise will have different spectra it is concluded that fan silencers and terminal silencers must be rated differently. Although it is recognized that all problems have not been solved tentative proposals outlining future single number rating methods for fan silencers and terminal silencers are given. It is also concluded that no classification system can be outlined until experience has been gained from a single number rating system.