scope:

This method is used to determine combined wheel-rail roughnessand track decay rates from rail vibration during the pass-by of atrain. By combining sound pressure measurement from the samepass-by, a vibro-acoustic transfer function for rolling noise isdetermined. The track decay rate is a vibration quantity thatcharacterizes the attenuation of rail vibration along the track fora given wheel/rail contact excitation, and thereby affects theamount of sound radiation from the track. Combined roughness is aquantity that determines the level of excitation of wheel-railrolling noise. It can be determined from vertical rail vibrationduring a train pass-by and the vertical track decay rate. Thetransfer function can be used to characterize the vibro-acousticbehaviour of the vehicle-track system for a given roughnessexcitation and in relation to rolling noise. Combined roughness,track decay rates and transfer functions are determined asone-third octave spectra. The method can be used for the followingpurposes: ? to measure track decay rates under operationalconditions; ? to characterize the effectiveness of noise controlmeasures in terms of combined roughness, transfer function andtrack decay rate; ? to compare the combined roughness before andafter noise control measures are implemented (thereby quantifyingthe effect of any change in wheel or rail roughness); ? to monitorwheel roughness during a pass-by, either of whole trains or partsof trains; ? to separate rolling noise from other sources; ? toassess a threshold for the rail roughness by measuring multiplepass-bys. The method is not for approval of sections of referencetrack in terms of acoustic rail roughness and track decay rates,which are covered by EN 15610 and EN 15461, respectively. Themethod is applicable to trains on conventional tracks, i.e. normalballasted tracks with wooden or concrete sleepers and onballastless track systems. The method has not yet been validatedfor: ? non-standard wheel types such as small wheels up to 600 mmdiameter, resilient tram wheels; ? non-standard track types such asembedded rail or grooved rail; The method is not applicable totrack with rail joints.