A simplified model for calculating the insertion gain of track support systems using the finite difference method

In the procurement of track support systems for railways planned in the vicinity of receptors sensitive to groundborne noise and vibration it can be necessary to specify parameters of components of the system in order to ensure that its in-service performance will deliver the required level of mitigation against the effects of groundborne noise and vibration. In previous comparable schemes in the UK it has been the practice to specify the performance of the track system in terms of Insertion Gain (IG). This is defined as the difference between the vibration spectrum at a reception point with the mitigating track in place, and with a hypothetically “very stiff” track support system. It is necessary to have a means of verifying that a proposed system is likely to satisfy the requirements and it is desirable to simplify the method of evaluation of predicted track perfor-mancebased on the stated parameters. A simplified algorithm for rapidly calcu-lating the insertion gain of a two-stage (or single-stage) resilient track support system has been developed using the finite-difference method. This provides a tool for evaluating the predicted performance of a variety of proposed track sup-port systems in order to compare it against the required specification.