Auto mute macbook on headphone removal I often listern to music on my macBook - when I unplug my headphones occasionaly forget to mute the speaker - so the whole office gets an earfull.  How can I set my mac to be muted unless headphones are plugged in. I'm interested to know if I can simply deactivate the built in speakers... 

This has become more obvious recently when I use a bluetooth headset or similar - I walk away from the machine forgetting the headset is attached and as soon as I get far enought away my computer starts making noise....
Unplug/disconnect your headphones, and mute the system volume. For added security, turn the volume all the way down. Plug in your headphones, and your volume should remain the same. The system will automatically switch between mute/no volume and the volume you have set for your headphones.

This is something that works on at least OSX 10.8 (I can't speak for sure on older versions of OSX), and a late 2008 or later Macbook. I tested it on both bluetooth and corded headphones.