macos - How to disable startup sound on a Mac?

Possible Duplicate:
Disable Mac startup sound

I tried to disable startup sound by pressing mute button during boot. Then I tried also StartupSound.prefPane application mentioned on several sites (http://www5e.biglobe.ne.jp/~arcana/software.en.html) but nothing works for me. The startup sound is always there without any change.

My iMac is new... bought in October 2010 and of course powered by Intel.

Answer

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...