I don't particularly care for the pop-pop-pop sound my MacBook Pro makes when I hit the volume adjustment keys, but it never got so annoying that I looked for a way to turn it off. Of course, once someone pointed out a way to disable it, I jumped at the chance. Thanks to this Cult of Mac post, I now adjust my Mac's volume in blissful silence.
There are two ways to silence a Mac's volume popping sound:
1. Head to System Preferences > Sound. Under the Sound Effects tab, uncheck the box for "Play feedback when volume is changed." This method will silence the popping once and for all.
2. If you like the audio feedback the popping sound provides and want to adjust the volume only on occasion in silence, you can hold down the Shift key when hitting the volume-up or volume-down button.
For more OS X tips and news, visit the MacFixIt blog.