I do not like the startup chime coming from the unit itself, especially when I have to reboot when others are asleep. On my 2006 Mac Pro it was always extremely loud. There was a terminal script that would silence it but it only worked for one or two reboots and then it started making noise again. The reboot sound in this machine is softer but it still makes noise out of a speaker I cannot control.
Maybe if I get an old set of headphones, cut off the wire and just plug it into the headphone jack?
Onyx has a parameter reset that disables Startup Sound. You can also disable via Terminal.
I recommend Onyx for all the things it can do. It basically is a GUI fronted program for Apple routines and terminal scripts.Get it here… www.titanium.free.fr/download.php?sid=69...808eee362b9ffa8ae215
This is freeware, donations welcome.
The control is found Onyx>Parameters>Login>Startup Sound>Turn Off.
Lastly, you can mute internal speakers prior to shutting down and chime should not play on startup, this is ok if you don't use the speaker, but you have to unmute if you use them. After ML (I believe) the Sound Preferences have separate volume levels of internal and external speakers.
Hope this helps,