Railways rolling stock - Validation is not a must, it is a support to reduce risks

Noise emissions and interior comfort of modern rolling stock are inherent technical performances analyzed during the engineering development process of train manufacturers. In order to fulfill requirements from railway operators, rolling stock manufacturers use different kinds of simulations during the design phase for different purposes like risk assessment, cascading of target allocations to subsystems, design validation before testing and virtual certification. Simulation can be a simple process using known acoustic analytical formulas or it could be a complex process with advanced numerical models. Whether it is simplex or complex, simulation needs a validation in order to get a measurable certainty of the results. Validation of simulations is a key aspect today but the complexity of the development process which requires several technical disciplines to work in parallel, short lead times and budgets available are challenges that vibroacoustic engineers have to cope with. Also R&D process tends to be shorter than before and the vibroacoustic engineer has at the end a final question: when should I stop validating my simulation model?