StartNinja starts up your Mac with silence and stealth.
Macs don't have a built-in way to mute or silence the system start-up chime. If you're in a library or coffee shop you don't always want that start up chime to play. Now you can silence the Mac OS X(10.7, 10.8, and 10.9) start up chime with StartNinja. It is a free and simple desktop utility that silences the start-up chime and will resume previous sound level after logging in.
Note 1: Does not work with iMacs
Note 2: The system start up chime is played through the internal speaker. If speakers or headphones are plugged in the system start up chime will still play.