I rented a house in a quiet neighborhood in Honolulu during most of the 70s, and my band built a rehearsing room in the basement by covering the walls with plywood, sheetrock, and mattresses (!). Worked great, and one day some guy from a block or so away comes by after he had trouble napping due to a strange (his words) low frequency sound, and he was relieved to find it was us making that sound. The bass just somehow wormed its way to him, and this was the only time any neighbor had said anything to us about hearing us play...over 7 or so years...