Rail vehicle source models within a virtual certification process
Invited paper
Bombardier Transportation CoC Acoustics
Wednesday 3 june, 2015, 13:40 - 14:00
0.1 London (90)
Abstract:
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.