They do make some noise. Is yours in the open or in a cabinet? Also go to the system information page and page down and see what the temp is, if it is over 50 deg c then the internal fan will be on high. The TiVo is ALWAYS recording, even in the standby mode. I have 3 of them in my HT cabinet, but it has a glass front so I dont hear it or I have gotten used to it.
I have a SA Tivo that is also in a closed cabinet, so I do not hear it.
That said, here is where you need to go for all things Tivo: http://www.tivocommunity.com/tivo-vb/
Regards,
Brian