Even if you take away the little red alert icons, flashing title bars, or beeping chat boxes, Facebook can be a huge distraction. This may not always matter, but disabling some of these notifications can help keep you on track later if you don't want to close the tab.
Disabling sound notifications can be done in just a few steps:
Step 1: Open the Settings menu in the top-right-hand corner of your Facebook page.
Step 2: Click on the Notifications option in the menu on the left-hand side. In the subsection "How You Get Notifications," click the On Facebook option.
Step 3: Uncheck the box next to "Play a sound when each new notification is received."
Note that this check box controls all of the notification sounds. And if you change your mind, you can always go back and flip them back on.
Now if only this switch could be added as a toggle to the front page of Facebook...