Hi I often study in a library with my MacBook. I do not want it to make some stupid sound in there and everyone look at me. What I do is just to mute it. However, this can accidentally be activated on the keyboard, and sometimes the muted state is not saved when I reboot the computer. I could deactivate the sound of every single application, including the error sounds in OS X, but this would be highly inconvenient when I want sound again. One solution that I like is to plug in ear phones in the MacBook. Then all sounds will always come to the ear phones regardless of the situation. But is there any good solution without the ear phones? What I would like to do is just to kill the the speakers temporary. OS X built-in solution or 3rd party app does not matter much as long as it is a solution. Thanks!