Rail vehicle source models within a virtual certification process

Invited paper

Ulf Orrenius

Bombardier Transportation CoC Acoustics

Wednesday 3 june, 2015, 13:40 - 14:00

0.1 London (90)

The Acoutrain FP7 European research project aims at developing procedures and calculation tools to simplify the present TSI noise test procedures. The overall objective is to reduce time and costs by developing methods for virtual testing. One main task is to develop assessment methodology applicable to the relevant source types, e.g. cooling fans and electromagnetic sources. Several challenges are at hand. Effects of source installation onto the train can be rather complex, modifying source power as well as directivity due to, e.g., screening. Also, the variety of vehicle source types requires that different assessment methods are considered and integrated in the process. Moreover, acoustic standards available for source power and directivity testing, e.g. ISO 3744, generally require echo free conditions and can therefore be difficult to apply for real vehicle sources. Due to their size and weight and the need for special electric supply systems and mechanical load arrangements, such sources are today tested in reverberant lab halls for which directivity measurements will be biased. In the present paper vehicle noise source modelling work carried out within the Acoutrain project is presented. When the source is surrounded by many reflectors, for example a radiating transformer behind roof shrouds, a single monopole with averaged transfer function is suggested. For a source with strong directivity placed in an essentially free space, a “box-source” method is recommended to take into account of the source directivity. The total sound power is in this case divided into five independent noise sources which are obtained via standard sound power measurement methods and certain data processing. Experimental verifications are made for several cases in laboratory and in the field. Good correlation between tests and modelling results are obtained for both approaches.

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