A FAST METHOD FOR PREDICTING THE ACOUSTIC BEHAVIOR OF COMPLEX HVAC DUCT SYSTEMS IN ROLLING-STOCK BASED IN FINITE DIFFERENCE METHODS

摘要

In the present paper, a method for complex acoustic duct network computation is detailed. The approach is meant to evaluate different acoustic solutions on rolling stock air distribution duct networks. Its main purpose is to simplify the acoustic design process, allowing reduced computation time and incremented accuracy on calculation results, if needed. The strategy is based on the complex network division in simple elements. The whole duct acoustic behavior is modeled thru single pieces coupled by continuity conditions. First, the calculation scheme for simple elements is presented. The latter is based on modified second order finite difference method, and allows using directly the absorbing material's normal impedance measured in Kundt tube, instead of the flow resistivity or alpha coefficient. Then, element coupling, acoustic characterization for a complex air distribution network and ducts' acoustic attenuation efficiency evaluation are discussed. Finally, results from one simple computation case and one experimental test are compared. The method is implemented in a Matlab code.