(to simulate what I mean, inhale, hold your breath, then suddenly force it out of your mouth against your throat, incredibly loud, and even disrupts my own breathing sometimes)

It could be some sort of tic that he struggles with. He's single handedly the reason that I started bringing headphones to work and my morale since he joined us has never been where it was before, except days when he's not in. In fact, on more than one occasion I felt in a really good mood, tried to reflect on why, and realized "oh! he's not here today!"

But how can one approach someone about something like that? It drives me insane and if I left the company tomorrow it'd be in the top 3 things that made me leave, but it could very easily be a medical condition!

I don't even want to bring it up with a third party because of how immature it sounds "That guy's breathing patterns make me upset", and because I have my own breathing problems (chronic nasal congestion), and sometimes my nose makes whistling sounds! I wonder how many coworkers have been annoyed to the high heavens since I started wearing headphones to cover up that guy's breathing, and was unable to hear my own nose whistling (if I hear it I can usually go to the bathroom and clear my nose a little and it goes away)

Sometimes I eat a late lunch or I eat certain foods and my stomach gets really noisy. And I don't mean passing gas, just the sound of my stomach growling loudly. I'm sure it's incredibly annoying to deal with, but how would someone approach me about that? "Hey, could you quiet down your stomach when I'm focusing?"

Stuff like that is why open offices are horrible. For every positive interaction I have because the guy I talk to is "right next to me", there's some glaring horribly stressful part that wipes out any gains. I think people use open offices as a crutch for poor communication culture anyways, the fact someone isn't "right next to you" shouldn't mean they have a hard time interacting with you when they need to.

To me it feels like a zoo, there's no privacy, almost never a quiet moment, and I'll definitely be reluctant to work at a company with open offices again. There are things between "every office is a sound isolated box with no windows" and "every desk is so close you can hear your coworkers food digest".