A Simulation Approach to Determine the Insertion and Transmission Losses of Unlined and Lined Ducts

One of the primary noise transmission paths in buildings is from HVAC equipment through ventilation ducts. ASHRAE Handbook-HVAC Applications provides tables for estimating the attenuation of lined and unlined ducts up to 10 ft (3.05 m) in length. The aim of this research is to suggest and validate a finite element approach which can be used to determine the attenuation of ducts of any length and dimension. The approach detailed simulates the standard measurement approaches for assessing duct attenuation. The duct air space, including the source and termination, is modeled using acoustic finite elements. Poroelastic finite elements are used to simulate the fiber lining, and the metal ductwork is modeled using structural finite elements. The model is used to determine the insertion and transmission losses of unlined and lined ducts. Predicted results are compared to measurements with good agreement.