I’ve found the sound effect caused by changing the volume on my Mac to be unnecessary at best and downright annoying at worst. Thankfully it’s very easy to silence, all without any special download or hack.
Silence the Sound Effect Permanently
If you never want to hear the sound effect there’s a setting in your System Preferences.
First, open up System Preferences and select Sound.
Under the Sound Effects submenu you’ll find a checkbox labeled “Play feedback when volume is changed.” Uncheck this box. That’s it!
Silence the Sound Effect on Demand
Perhaps the sound effect doesn’t annoy you to the point of wanting to turn it off completely but you’ve had situations crop up when it would have been nice to adjust the volume silently. In this case simply hold down the shift key while adjusting the volume to prevent the sound effect from playing.
Strangely enough, if you’ve already turned off the volume permanently then adjust the volume with the shift key held down the popping sound will resume on command. I don’t know why you’d want to do that, but the option is available.