Squealing noise abatement techniques in athens tram network

Abstract

This article presents various operating systems, developed and implemented at the Athens Tram network to reduce the airborne noise emitted in the sharp curves of the tramway. From the first days of the network's operation (Olympic Games 2004), the problem of producing airborne squealing noise in certain sharp curves of the tramway was revealed, with a series of complaints to be recorded from residents in certain urban areas, regarding especially squealing noise emissions introducing annoying peak levels especially during evening & night hours. The problem was treated, initially, by coating the tracks with biodegradable lubricant, at sharp curves, where it appeared that friction phenomena were significant. The coating has been performed manually for some years by maintenance personnel of the network, providing suitable results by the acoustic measurement program. Even though this intervention has produced positive results, as well as alternative technical solutions relating to the installation of mechanisms for automatic lubrication of rails with special friction modifiers, they were proven not to be feasible economically. Therefore an automatic rail wetting system was implied, containing sensors to detect approaching trams, water supply, timer, solenoid valves, pipes and common irrigation vaporizers. The system is quite simple and is implemented using common components of retail trade, many of which are already used in existing irrigation network of the tramway, while the maintenance does not require trained staff, it is performed by the staff of TRAM SA and in connection with the maintenance of the irrigation network. The results of recently executed detailed noise monitoring programs, performed by the University of Thessaly (Faculty of Civil Engineering), are presented for both implemented technical solutions that indicate significant reduction in squealing noise emissions.