There is a solution and it is not difficult, but it takes some working. You need a sound editor capable of opening the .mel archives. I think GoldWave is available in a demo version (Do a google search) and works for that. Then go to the /SFX directory and see which file is the Destroyer ping (Knew it long ago but forgot it, sorry

) then lower the volume of the file, save, and you are ready to go.
May be the guys over at
www.subsowespac.org can give you a more precise advice on which file it is, but some of them also visit frequently this forum so you might get help here.
Hope that helps