Just wondering, what program are you using to edit the audio files?
if you mean the way openBVE plays the audio files while the train runs, there was program for editing openBVE trains on trainsimframework's website for download, but that site is now unavailable. If anyone wants it, I may be able to get it on this site if the mods deem it appropriate.
Keep in mind however, that you can't just use that one program to perform modifications such as this one. It involves knowing which files to transplant, which ones to delete, how to handle a sound.cfg file, and which values are needed, and also how to manually change the motor/electric brake sound commands directly from the train.dat file.
EDIT: Although the main site has closed, the archived version is still up and easily navigatible, despite the fact that none of the downloads have been archived:
http://web.archive.org/web/20090626235359/http://openbve.trainsimcentral.co.uk/develop/index.html