Come on guys...let's not attack the OP and turn this into a p!ss!ng contest.
There are people who grunt because they're cranking iron and really getting into their workouts. LOL, in my own home gym there are times when I'm yelling, screaming and singing along to System of a Down "Let the bodies hit the floor"...and I'm all alone and not looking for attention. It's just part of getting psyched and cranking it up a notch. In martial arts the "keya" is an audible expression that adds to the power and exertion. Some people are audible, others aren't...but in all cases the guys who walk the walk do their thing regardless of what the posseurs are doing and a good MP3-player can put your in your zone and remove you from others (good suggestion!)
At the same time, there are plenty of attention punks whose verbal exploits are entirely intended to draw attention and it's all part of a show....and I'm pretty sure the OP was referring to these such posuers. Hey, confident guys can get annoyed too.
Do what ya do and don't worry about others....at the same time, there are plenty of people who can be annoying, and some of them are downright fun to mock because they're just too funny, like swollen-chest dude, bandana-man, rock-star and others.
On that note, there's a trainer at my gym who attends the Sunday morning spin-class...this gal sits up front, stays in a low race position (cause ya know how aerodynamics can affect you on a stationary bike) and she gets all into it....she's known for making these really long & loud "ohhhhh-yeeeeahhhhhhh" scream-moans. You don't have to imagine what this chick is like in the bedroom, cause she's verbally going at it right there in class. I find it disruptive because it cracks me up. Is it for attention? I don't know...but like a verbal beacon screaming-out in the night, she just permeates the room with her verbal discourse.