MacMundi

This sound (named "Apple Chime") is an Apple tradition, and some veteran mac users are even proud of it. It is in fact a message telling everything went fine during the startup process. But for many users it is just an annoyance, specially if it wakes up your whole family the first time you decide to use your Mac early in the morning. Officially, the only way to stop that sound from playing on startup is by turning off the computer's audio every time you shut it down. But nobody wants to do this over and over, so we desperately need a better solution.

Luckily THERE IS another solution:

1) Go to this website and click on "download". Save the file "StartupSoundPrefPane.dmg.gz" on the desktop. Note: make sure you're downloading version 1.1 or higher, as older versions do not work on Intel Macs.
2) Double-click the file to extract it. A DMG file with the same name will be created on the desktop.
3) Double-click the DMG file ('StartupSoundPrefPane.dmg') to open it. This will "mount" the installer, i.e., a new icon will appears as if the installer was a storage device. Then, the content of the installer will be exhibited automatically in a Finder window.
4) Double-click the "StartupSoundPrefPane.pkg" icon. The installation will begin. Follow the instructions on the screen, clicking the appropriate buttons.

When the installation finishes, a new icon named "Startup Sound" will be available at the "System Preferences". Click on it to adjust the desired volume setting for "Apple Chime". From now on, your Mac will no longer disturb your family's peace!