would giving him a reward for talking quietly (ie not shouting) work? Murray used to bang his cot and put the light on/off for his daytime nap - if he lay quietly, keeping the light off (you are best to tell them what behaviour you want to see, rather that what you don't want to see) he would get a reward (ie watch a specific programme I would record during his nap, or something else he can do/get as soon as he wakens up)