Just adding for the record, that adding the Mute option to the Preferences…Sound panel has greatly helped.
As a workaround until such time as Vassal allows per module sound volume control, there are OS and 3rd party app level controls that users might try.
There are one or two other issues that Vassal might improve on, discussed elsewhere. wav files in quick succession don’t buffer (in fact,cancel each other); mp3 files on the other hand are additive (exacerbating the volume issue). At present, module controls over this can get over complicated. This is why I’ve suggested that GKC includes sound suppression, just as it does report suppression.
Mark