Mouse squeaking constantly

Question
My friend has a little mouse that is constantly chirpping, squeaking, or chattering. She also does it very loud. She seems happy in her home and gets along great with the other two mice in with her, so I'm not sure why she constantly "talks" the way she does. We actually got her for free from the pet store because one of her ears was nearly missing and the other was half gone. They were both perfectly healed and she was very active and looked otherwise healthy. I'm wondering if she makes so much noise because she can't hear herself or if it's something else. She stops periodically, but not for long, and she doesn't do it while she sleeps. Do you know what may be causing this?  

Answer
Dear Rebecca,

The chirping has nothing to do with her ears.  One reason a mouse can chirp or chatter is that it once had a respiratory infection which, in effect, lowered its 'voice.'  Mice actually squeak all the time but too high-pitched for us to hear.  When they have been sick their squeaks are in a pitch that we can hear.  I like it because I know when the mouse is talking to me.

Thank you for taking the little mouse in.  I always like the handicapped or unusual mice best.  Give her a little extra attention and you'll have a special mouse in your hands.

squeaks n giggles,

Natasha