Auralisation of train pass-bys for virtual reality demonstration of combined noise mitigation measures

Railway noise can be reduced by various mitigation measures and combinations thereof. However, it is difficult to assess their combined effects and to communicate the options to stakeholders. For this, auralisation is a promising technique that can support communication and decision-making, and enable psychoacoustic evaluations. This paper presents a new physics-based auralisation model for train pass-bys that considers combined mitigation measures. The measures include acoustic rail grinding, avoidance of wheel flats, wheel and rail dampers, rail shields, mini barriers and classical noise barriers. Pass-by parameters such as train type, speed, track design and observer location can be selected. The proposed model includes contributions from rolling noise, impact noise, traction, auxiliary systems, and aerodynamic noise. The main novelty of this work lies in the improved time-domain synthesis of rolling noise. The sound radiated by each wheelset is modelled by multiple moving point sources. For the sound radiated by the track, a new hybrid model is proposed that consists of a combination of moving and fixed equivalent sources, reflecting the structural wave propagation in the rails. Separate source contributions for radial and axial wheel vibration, vertical and lateral rail vibration and sleeper vibration are considered using TWINS-based computations and an improved description of rolling damping. First comparisons of synthesised and recorded train pass-bys showed a very good agreement and a high degree of realism. The auralisations were coupled to an immersive virtual reality environment that allows for an interactive audio-visual experience of different train pass-by scenarios and to demonstrate noise mitigation options. The presented models were implemented in two software tools that are described in this paper and made available. The tools have already been successfully used in public demonstrations at international exhibitions and information events for residents.