7. Outlook

We have focused on environmental acoustics and interior comfort, mainly on TGV equipment, for the following reasons.

• All known acoustic sources can be found on this equipment, in particular the aerodynamic source, the travel frequency,

• The source of rolling noise is basically the same for all equipment. We have seen that its level varies greatly with speed and wheel condition. However, we have briefly touched on this issue for freight equipment: wheel wear is a function of the type of braking and its aggressiveness on the running surface, which increases between disc brakes, composite shoe brakes and cast-iron shoe brakes. The difficulties that limit the improvement of freight equipment are essentially economic. Replacing cast-iron brake blocks with composite brake blocks requires wheelhouse modifications on a large number...