Sometimes it feels like the office is your home away from home. Just as you don't choose your family, you usually don't have a say as to which coworkers are situated close to you. If one or more of these coworkers are loud and disruptive, not only could it detrimentally affect your productivity, it can create stress and tension between you and your fellow employees.
Here are a few approaches you can take to work toward a solution.
(1) Try to Mitigate from Your End
See if this loud, disruptive coworker is something that seems to only bother you. Some people are more sensitive to regular noise than others, and there's nothing wrong with that. You could try a pair of earplugs or decent quality noise canceling headphones, and maybe ask your work for a headset extension for your phone.
If you are allowed to listen to music while you work, remember to wear earbuds or headphones so your music doesn't disrupt other people. Also, remember to take them out of your ears before speaking so you don't end up inadvertently raising your voice when you talk. After all, fair is fair.
(2) Request Quiet From Loud Coworkers When You Need It
If you are about to take an important phone call or meeting at your desk, people are usually good about hushing a little if you politely ask those around you if they would mind keeping it down for a few moments (and explain why). Another option is to make a sign (here's where a sense of humor will help a lot ) which you can put in a visible space to signal that you need some quiet. Try something like, "Do Not Disturb - I'm disturbed enough and on an important call!"