technical help pl....virgin tivo box

..recently replaced the old non hd standard box with the above . now hd benefit on tv and picture , sound all fine .i have noticed however that when sound v low or 'mute' on ( eg , to cut out mick fitz ) the box has a slight  background tapping or rumbling sound. when i put my hand on the box you can feel a slight vibration . is this normal ? the old box didn't do this . also , my internet box thingy ( black , about 8 ins high with a blue virgin symbol ) with the little flashing lights on the side is only inches away from the box .  dont know if this matters , as you can tell i'm a total idiot when it comes to such matters so any serious advice would be appreciated .
i'm off to the pub now but will check the forum tom . cheers .