With numpties like these you have to fight fire with fire, find out when they sleep and if he's on shift then it probably won't be when you are. Then put your stereo on full blast under their bedroom and go to work, leave it on all day. That night they'll complain, then you say," I tried to negotiate but it was clearly beyond your limited IQ, therefore if I get no sleep you get no sleep, capiech?. Tell them to get a mat in the kitchen/bathroom and walk on that. Really do it, every time they make a noise the old man get's no sleep. Even dumb animals learn eventually.
This happenned to me once in reverse, I was horrified when I realised the noise it made downstairs, I just got a mat in the kitchen, the noise is because the floor is hard.