Noise Elimination and Reduction Structure for Tram Air-conditioning Return Duct

Objective The noise generated by air-conditioning system is a primary source of static noise in trams, with most of the interior noise originating from the air-conditioning supply fan. Aimed at reducing the noise in air-conditioning duct, research focusing on the duct structure is carried out to design a low-frequency, broadband noise elimination and reduction structure. Method Noise reduction optimization is performed on the noise transmission path of the air-conditioning return air duct in trams. Referring to the original air return structure, a composite noise reduction device is designed, which is based on a perforated plate combined with porous sound-absorbing materials, to mitigate the fan noise transmitted through the return air duct. A statistical energy model that includes the return air duct and the fan noise source is established. Combined with the theoretical calculation of sound absorption structure, the noise reduction characteristics of diversion and noise elimination air duct are calculated and analyzed. Result & Conclusion The adoption of a flow division and noise elimination duct effectively decreases the noise transmitted by the fan. By building a test platform for air-conditioning duct, the feasibility of using the noise reduction duct to eliminate tram air-conditioning system noise is validated.