Contribution
The effects of uniform motion on the sound radiation directivities of train wheels
* Presenting author
Abstract:
The sound radiation by vibrating wheels is one of the key components of the pass-by noise of trains.In this paper, we examine sound radiation by moving train wheels by means of numerical methods focusing on the effect of the motion on the source directivities.Most studies model the sound radiation by the moving wheel by applying stationary radiation transfer functions (direction characteristics) to a moving observer model.The vibration modes of the wheel are computed using the structural finite element method, exploiting the cylindrical symmetry of the geometry.Vibration mode shapes prescribe normal velocity boundary conditions of the wheel, whose far field sound radiation characteristics are evaluated by the convected boundary element method (BEM) in a half-space arrangement.We discuss the formulation of the problem as well as some important steps of the implementation, such as the mitigation of the problem of irregular frequencies of the BEM.The resulting directivities of the vibration modes are analyzed and compared at different pass-by velocities.Finally, the total pressure field at a stationary receiver is evaluated with assuming that vibrations in the wheel are excited by the interaction with the rail having a prescribed roughness spectrum.