How to disable startup sound on a Mac? [duplicate]

Solution 1:

You can disable the startup chime with shell scripts: ( Tested on 2008 MacBook w/ 10.6.4 )

Create a shell script named off.sh in directory of preference. In this example the script resides in /Users/youraccount/Desktop :

sudo emacs off.sh

Enter this code in the script:

#!/bin/bash                                                                     
osascript -e 'set volume with output muted'

Make the script executable by root :

sudo chmod 755 off.sh

Enter this code in Terminal :

sudo defaults write com.apple.loginwindow LogoutHook /Users/youraccount/Desktop/off.sh
sudo defaults write com.apple.loginwindow LoginHook /Users/youraccount/Desktop/off.sh

You may not need to have both hooks, but it definitely works when both are created. Your startup chime should be muted on reboot. The caveat is that you have to unmute your volume each time you login...

Solution 2:

Disabling the POST is a bad idea. The Power On Self-Test is there to let you know if any serious hardware issues are detected once the machine begins to boot. However, the methods you have already tried are correct. It is possible that Apple has made modifications so that you can no longer hold down the mute key to disable the POST sound and I haven't been able to find a date that shows when the StartupSound preference pane has been updated. It could be that your iMac is too new for it to work.