I really don't have any idea about the loud noise issue, but I do know that my Rosy barbs have NEVER appeared stressed. I got them in the beginning, when I knew nothing, and I had them in a WAY overstocked tank with Tiger barbs. ALL of the tiger barbs were stressed and caught ick, and one of them even developed a bad fungus. They were all removed and placed in the hospital tank for treatment, and the Rosy's were moved into a bigger tank. Those poor Rosy's have been through a LOT of stress-inducing situations, and have NEVER appeared bothered by it, always swimming happily.