Two models are developed, one in the time domain and another in the frequency domain, to explain when a wheel/rail noise generation model requires the inclusion of discrete supports, parametric excitation, and the nonlinear contact spring. Numerical simulations indicate the inclusion of discrete supports to describe low frequency response, and also at higher frequencies, especially where the rail is very smooth or has a corrugation/wavelength corresponding to the pinned-pinned frequency. With a corrugation, it may become essential to include the nonlinear contact spring, as contact loss occurs at high corrugation amplitudes. As nonlinearity causes force generation over a broad frequency range, some contributions excite wheel resonances, resulting in high radiation levels, that require the inclusion of wheel/rail nonlinear effects and parametric excitation for accurate prediction.

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For optimization of a low-noise track system, rail vibration and noise radiation needs to be investigated. The main influencing parameters for the noise radiation and the quantitative results of every track system can be obtained using a calculation model of generation and radiation of railway noise. This kind of model includes contact modeling and the calculation model of the dynamic properties of the wheel and the rail. This study used a nonlinear wheel/rail interaction model in the time domain to investigate the excitation of the rolling noise. Wheel/rail response is determined by time integrating Green's function of the rail together with force impulses from the wheel/rail contact. This model and the results of the study can be used for supporting calculation with the conventional model by an addition of the contributions due to nonlinearities to the roughness spectrum.

The most difficult problem concerned with railway noise generation is the process occurring in the contact region during rolling. The following computation efficient time domain model determines the vertical rail deflection by use of Green’s function of a periodically supported beam. Nonlinear Hertzian contact mechanics are used, less realistic, however, than a discretized contact region allowing for rough surfaces. The wheel is as yet a rigid mass. More advanced contact and wheel models can readily be included later. Calculation results include the following observations. The contact force peaks sharply precisely above the support points, followed by a short loss of rail–wheel contact, also for smooth rails. Vibrations of the rail pinned–pinned mode are impossible to eliminate by removing surface roughnesses, because the excitation is above all caused by forward wheel velocity together with discrete supports. The response amplitude increases with forward velocity. Optimum pad stiffness depends on corrugation amplitude. These new findings should be considered when trying to noise optimize track constructions.