Determination of Lined Duct Insertion Loss and Breakout Transmission Loss

Heating, ventilation, and air conditioning (HVAC) engineers usually rely on the tables in the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Handbook to determine the insertion loss and breakout transmission loss of unlined and lined ducts. Though the Handbook is often adequate for building design purposes, the Handbook does not account for the wide range of duct sizes, configurations, and lining types. Hence, a simulation approach is desirable. In this paper, finite element simulation is applied to HVAC ducts and results are compared to measurement with good agreement. Three different material models are used for the sound absorptive lining and insertion loss results are in good agreement regardless of the material model selected. Breakout transmission loss is also predicted and compares well with equations in the literature. With a qualified finite element analysis approach, more complicated HVAC duct configurations and attenuation schemes can be investigated in the future and the ASHRAE Handbook information can be improved and expanded.