adjust/mute the volume of your Mac's startup chime. Double-Click "Psst!" in the Finder to adjust the volume settings.Psst is a faceless free tool that lets you

At some time/place you'd better start/restart your Mac without a chime. Just copy Psst to your HD and launch it once, no more installation needed at all.

Psst is a faceless application that does not appear anywhere. At next start no chime will disturb anybody anymore. To get the chime back again, just remove Psst! from the user's login items. And launch Psst! again anytime to get back to silence.