Dad (early 70s) is making weird sounds constantly. What could it be?

After some prolonged time with dear old dad in the car recently, I noticed he constantly makes weird little sounds and vocalizations when things are quiet. I don't think he has any idea he's doing this. What gives? They sound like a pretty steady stream of the following:

* Quiet Throat clearing
* Mmming
* Loud verbalized swallowing
* A quiet "uh" stutter, like he's about to speak
* Vocalizing small sounds while breathing
* Lip smacking

It's basically like whatever he's doing with his throat, he's making vocalizations outloud to go along with it. It's like the "tennis grunt" but instead of happening every time he swings a racket, he's making tiny noises every time he swallows or moves his mouth or breathes.

Or you know how some people can choose to over-vocalize a sneeze? It's like he's doing that with every micromovement in his upper respiratory tract.

I find it super distracting, annoying, and to be honest, a little bit gross.

But you know, he's my dad, so I want to be sympathetic. It doesn't sound uniform enough to be a tic. He's a smoker and sometimes coughs a lot in the morning. He's fine in conversation and doesn't seem to have hearing problems, but maybe he doesn't hear himself doing this weirdness and doesn't realize it??

What the heck could this be?