DESIGN OF AN ON-BOARD NOISE MITIGATION SYSTEM FOR A TRAM VEHICLE

This paper presents the results of the design of noise reduction measures for the Florence “Sirio” Tram. This activity was performed in the framework of the Life “SNEAK” project (“Optimized surfaces against noise and vibrations produced by tramway track and road traffic”), LIFE20 ENV/IT/000181. Specifically, bogie skirts - i.e. noise barriers positioned on board of the vehicle, directly connected with the tram bogie - were designed and optimized to mitigate noise emissions from the wheel area. A test campaign was carried out to acquire sound profiles describing the emissions of interest of the Sirio tram. Repeated measurements were performed to measure: i) rolling noise emitted by the bogie while the tram is moving along a straight line at maximum cruising speed (50 km/h); ii) braking noise in a full stop; iii) squeal noise, which happens when the tram passes through a tight curve in absence of lubricant. A customized solution, which implements a sound-insulating and sound-absorbing panel placed in front of the wheel, was designed to replace the existing set of wheel covering panels. Such a device includes an extended barrier towards the ground to limit the noise emission area to a minimum. The preliminary results obtained with the proposed solution, which was tested in a simplified scenario, are discussed in the paper.