"We all have them: Irritating coworkers, so, what's the best way to deal with them?
One is direct. You can actually go to the source and a lot of times people don't understand how irritating they're being, so if you say in a very kind way: ""hey, I'd appreciate it if you just keep the volume down when you're talking to your mom in the cubicle next to me"" they'll be apologetic and they will appreciate the fact that you're pointing it out to them, and probably try to change their behavior.
The other tactic you can take is more a non-verbal, more passive. So instead of asking them to tone it down on the phone, it's to put a pair of earphones in, so you're not distracted by their conversation. That's the more non verbal, passive way of approaching it. And chances are they're gonna see the fact that you're wearing the earphones and may think to themselves ""hey maybe I should lower my volume when I'm having a conversation with a friend or a family member while I'm at work""
So in dealing with an irritating coworker you can either learn to live with it or you can deal with it directly, your choice.