[RetroTechie]

Yeah. It's just a hunch, but I suspect the brain has a tendency to create signal by itself if 'outside' drops below certain levels.

Such self-generated signal may be more annoying than low level external noise.

Over the past summer, it's been mosquito sound for me. There'd be a few, I'd kill 'em, and then sound of the last one would keep 'ringing in my ears' even though I cleared the space of mosquitos.

But hearing is complex. Things like diet, exercize, blood pressure, history of exposure to loud noise, drugs, age etc all play a role.