Tinnitus (often called ringing in the ears, though it can be a variety of sounds, volumes, and patterns) is noise produced within the ear rather than noise originating from the environment outside. Sometimes it is only internal -- no one else can hear it -- but there are types of tinnitus that others can actually hear.
How weird is that. So I'll mark this down along with the fact that rabbits eat their own shit well their own cecotrophes. I never knew either of those things.