Originally posted by MarkJerling The rattling noise is most likely the camera's shake reduction system working. It could be that the noise is more amplified with that particular lens. To help us check if that is the case, I suggest you take a video clip with your phone or another camera and post that to Youtube and link here, so we can hear what you hear.
Also, can you confirm if it makes this noise if you turn the camera on with no lens attached?
Kind regards,
Mark
Could it possibly be the dust removal option?
If mounting that lens on another KP produces no noise, then it's not the lens, so all there's left is your camera body.
Go into the menu (it's possible that your brother has Dust Removal turned off on startup so there'd be no noise), look for the dust removal option, and turn it off for both startup and shutdown (on and off).
Now try turning on the camera with the lens attached and see if you still hear any noises. Do you have horizon correction on? Composition adjustment? If so, turn those off as well. Basically, turn off anything that may cause the sensor to move (including Shake Reduction). If you can, look at your brothers KP settings in the menu and copy them on your camera to a custom user setting so the changes can be tested and removed afterwards (unless you want to keep his settings), is the noise still there or is it now gone?
PS: I notice in your post you say when you turn the camera "in", did you mean when powering it on, or when you rotate/angle the camera?