Under certain conditions my monel water tanks act as a drum set. The volume and variety of sound is amazing. They are cylinders, under the v-berth. Probably not baffled, but retrofitting would not be easy. My wife was not pleased to hear this "music" until 0130. My only idea is to wrap them in foam or replace them. I also think I remember something about putting a weight in the middle of a panel to reduce vibration. Most of the sound must come from the ends. Has anyone solved this problem?