I’m thinking it’s a multi mic+. And yes it’s a type of microphone. I’ve only got mine this week so I’m not really sure how they work. (I’ve not read the instructions as yet) @MDB or @Raudrive will be able to explain how they work for you.
Does your wife have a hearing aid in her other ear? Has anyone suggested a Cochlear implant in her deaf ear? It could be worth a consult with a CI surgeon. I’m not sure if that’s even a possibility with her TBI. But an opinion from a CI surgeon could be an idea for you both.