An old man with terrible hearing went to a hearing doctor one day. The doctor found a pair of hearing aids that could give him perfect hearing again. He put them in and the old man went home to his family.
A few days later the old man came back to the same hearing doctor.
The doctor said,"Your family must be so excited that you can hear well again!"
The old man replied,"Actually I haven't told them yet, I just sat there listening to them talk when they think I can't hear."