A friend who has hearing aids told me about induction loop technology, which is used in some theaters, museums, etc. A large loop of cable around the floor induces the proper signal in special hearing aids so that the user can hear things others can’t. He’s wired a large loop of wire around his office so that he can use induction to hear music through his hearing aids, remaining silent to other people. Apparently, there are also bluetooth hearing aids that work with cellphones, etc. Many interesting possibilities come up.