Question about custom horns

[rwk]

I tried putting my own recording of a horn into a copy of a horn sound folder, and the horn doesn't play in game. I used Windows Sound Recorder to record the horn from a youtube video, and put the sound file into the folder, named it the proper name (horn, etc.) entered Trainz and the horn won't play. The bell plays as it was already there, it was modified from a downloaded horn, I changed the horn but not the bell. Does the horn sound have to be WAV, or a certain bitrate to play? Does it matter how many seconds the sound is? It's about 7 seconds. Please help me, thanks, Robert