It’s a bizarre sensation but I wonder if it’s actually rather common.
The most interesting related thing I've experienced is hearing an unexpected noise in the night (once it was a mouse in my room) and being woken up by whatever part of my brain monitors that stuff, and then having the really visceral sensation of the unexpected sound being played back to my now conscious brain to try and give context.
I don’t suppose you’re also a very visual person, who prefers to solve math problems geometrically rather than algebraically, etc. There may be a link between that buffering and the ability to turn abstract shapes in one’s mind.
My diagnostic ADD testing was inconclusive because I was able to excel at working memory and shape tests because I am able to hold onto a ton of information if I can write it on my mental blackboard etc.
When I'm listening to a conversation, what I'm hearing often produces a stream of involuntary visuals representing related information and subjects, like I have a mental background process showing me flash-cards of possibly useful information.
I also have the issue where someone will talk to me and there's this delay where I often appear to be non-responsive for a moment or two until my brain spools-up and then I mentally lock into the conversation.
Anyway, if you have any references or additional learnings you've found related to this topic, please share.
In a small enough buffer time, I can catch up and context switch and “hear” what was said… but after a certain point, it’s gone (probably out of working memory).