Transmission loss simulation of treated HVAC ducts for railway applications

摘要

This paper provides a method for assessing the acoustic performance of complex HVAC duct systems. It includes a theoretical description of acoustic duct modes and the way to handle them in a finite element context to produce a purely non-reflecting boundary condition. The method is applied to an HVAC system used in a railway equipment. The transmission loss i.e. the ratio of incident to transmitted acoustic power (TL) is computed as well as the acoustic field in each sub-component. The geometric dimensions of the inlet and outlet sections directly drive the TL, primarily by controlling the frequency at which higher order duct modes appear.