The really BIG question here is... why on earth are you hanging out around bathroom doors listening to guys do that??? What kind of weird sicko are you???
Okay then... why on earth are you hanging out in men's room stalls listening to that sort of thing??? Never mind, I don't want to know cause then I'd be creeped out anytime there was another guy in another stall!!!
"Why do guys sound like they're giving birth on the toilet..?" Is all I see in your question! Maybe you should take another look at it!
They are on their thrones there...hahahaha
Seriously, we are in generall much less self conscious about our bodly functins, so bit of ex<x>pression in the toalete, which may be overheard is not a problem.
LOL. I don't know about sounding like it but they sure can take their time in there.
Hehehehe, I don't think we grunt and groan the same at all.