A few weeks ago I took a (successful) leap of faith and was able to use the ADPCM software to change the bell sound in my MTH New Jersey Transit Ps3 F40. Using the ADPCM software allows one to edit the .mth files and specifically customize loco sound-sets. If one just wants to simply swap original sound files that are downloaded off of the MTH website, than the consumer loader will do the trick.....But if one wants to swap individual sounds within the .mth file, than the ADPCM tool is a great way to do so.
There are some very detailed YouTube videos explaining this process. ADPCM is to be used at one's own risk and I personally recommend downloading a copy of the loco's original sound file just in case a sound restoration is needed.
Plus 1. Love this program!