My uBPDw does the exact same thing. I have a mild HF hearing loss, not enough for hearing aids. When I was diagnosed I told the doc, "So in other words, just enough to annoy people who talk to me?" and he laughed and said yes, that's about it.
She knows this, we have discussed it, but she will purposely lower her voice to get me to ask her to repeat, and then get annoyed when she has to repeat something. She does NOT have a quiet voice; she has one of those voices that enters the room before she does most of the time

Only when she wants to try to throw me off balance does it suddenly get very quiet.
She also does not normally talk to herself, unless she is dysregulating and I am in earshot, then she keeps a running under-the-breath commentary of everything she "has to do," etc.
I am trying to set a boundary--"If I don't hear it, she didn't say it," for her and for myself, and stick to it. It's an old habit on my part, so it's hard to break, but I'm working on it.