I wonder too if it might be some sort of cognition issue..
foggy brain type of thing..??
which could go back to the brain injury.
Is it only sounds that are a problem, or comprehending what is being said?

When my RSI/TOS was at it worst I had trouble following conversations in a crowded places or large groups, I couldn't multi task at all.
I had to focus on one thing at a time, it was kind of like I had ADD & a bit of Alzheimer's for awhile..