Laboratory methods for testing the performance of acoustic rail dampers
Résumé
Several types of rail damper are now commercially available to reduce noise radiated by railway track. These dampers, attached to the rail between sleepers, increase the attenuation with distance of vibration transmitted along the rail (decay rate). Currently, there are no standardized procedures to measure the effectiveness of these dampers without the need for their installation in a track. Track decay rates of damped freely supported rails have been measured using two proposed methods: (i) for short rails (4-6m length), at low frequency from the modal properties of the rail, and at high frequencies directly from point and transfer response functions (FRFs) at either end of the rail; and (ii) for long rails (15-32m), by integrating decay rates derived from FRFs measured at intervals along the rail. Results from four test institutes show generally good agreement between the two methods for three different damper designs. However, at some frequencies substantial inter- and intra- method variability is evident. Sources of this variability are identified and are discussed. Further tests conducted on a 32m test track show that decay rates of damped track can be reasonably determined by summing decay rates of the free damped rail and those of the undamped track.
Domaines
Acoustique [physics.class-ph]
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