In the quest for quieter and environmental friendly transportation systems, electrically powered trains are well placed to comply with stricter user requirements. However, electrified lines are not always available, and in some cases diesel engine powered train is the only option.
For these trains interior noise as well as exterior pass-by-noise levels must be carefully monitored. A common strategy is to control noise emissions passively, adding absorbing materials to the sidewalls of the passengers cabin such as to reduce the noise transmission in cabin, or with engine encapsulations that improves transmission loss from engine compartments.
But, passive means are not effective at low frequency range, as they would require thick layers of lining material to achieve the required noise isolation performance. Alternatively, active noise control technology can be used to optimise noise reduction by supplementing acoustic isolation performances at low frequency.
The purpose of the current study is to implement a hybrid model of the under floor engine compartment of a DMU (diesel multiple unit) train based on the combination of experimental data and numerical models. The hybrid model allows simulating noise reduction performances that can be achieved by superimposing passive and active noise reduction strategy in the engine compartment.
