After a while of using a Mac, system sounds that play every time you do something wrong will get annoying. Most of the time, as and experienced user, you will know that you have made a mistake. You don’t need an annoying dong, to accompany it. As well as this Automator, and Apple Script to some extent, usually make an annoy dong every time it moves through the script. You can turn these off easily with only a couple of clicks. Save yourself some sanity.
To switch off System Sounds, open up System Preferences and click on Sound. Under the sound effects tab look at the bottom of the screen. The volume slider controls how loud a sound effect will come out.
If you move the slider, Alert Volume, all of the way down to the bottom it will turn off all of the alert sounds. This means that error messages, and anything else that would make a noise will not appear with the slide volume at minimum. From this section you can also turn off Front Row volume noises as well as feed back on volume changes.