Soundz
The Soundz utility can be used to listen to engine and horn sounds for Trainz assets with a reasonably good representation.This does not include an audio editor - if you wish to edit the sounds, get hold of a tool like Audacity or similar.
Current version of this tool is 1.03, released on the 27th March 2015.
Download this tool from here
Additional Tools
No additional tools are required for this program.
Previous Versions
Version 1.02 - Download here
Version 1.01 - Download here.