I played with the file and made the siren delay for a few seconds after the torp hit.
http://rapidshare.de/files/33877930/...osion.wav.html
The only problem Ive found is if you hit a ship with several torps quickly the alarm can get duplicated and sound a tad off. If there were some way of making this wav only play during the first torp hit on a ship I think it would be perfect.
Nice overall idea!