Experimental Characterization of the Vibro-Acoustic Behaviour of a Switch

The work presented in this paper is part of the SNCF project BPS (noise from singular points), in which the noise emitted by steel bridges, joints and switches are investigated. Switches and crossings are numerous in urban inhabited areas. From a dynamic point of view, the switch is a complex track component where many wheel/track interaction phenomena are combined. In this complex physical context, the objective of the measurement campaign presented in this paper is to identify and characterize the sources distributed along a specific switch that contribute to the radiated noise. The measurements were performed in December 2012 on a switch (and also on a reference section) crossed by mixed traffic, equipped with accelerometers (for track and ground-borne vibration) and microphones. Compared to the reference section, the track characterisation by impact hammer excitation shows a lower stiffness under the crossing nose and a higher stiffness in the 150-500 Hz frequency range under the switch rail. The amplification due to the wooden sleepers is responsible for a rolling noise increase in the same frequency range. The crossing nose and the insulated joint are impulsive sources with a given power. For the pass-bys generating a high noise level at the reference site, their respective noise contributions are negligible.