Well, good news, bad news on this. It appears that installing the water hammer arresters did diminish the sounds of the pipes banging around in the walls, but they still make some reasonable racket in the newly remodeled master bath. I installed them on the washing machine itself, as the instructions indicated rather than to the bibs coming out of the wall. So it's a step in the right direction, but didn't totally fix the issue, at least in master next to wear I sleep.