From less than 48 hours ago:
http://www.mac-forums.com/forums/showthread.php?p=486094
Anyway, that "annoying" sound lets you know that everything is okay with your computer. It's actually the result of a bunch of hardware self-tests the Mac runs on its motherboard, RAM, video circuitry, etc. at startup. when you hear the standard Mac startup chime, that means all the major subsystems have been tested and have passed; if any of the tests fail, you'll hear something else at startup. If find some way to bypass it, you could end up missing an important post sound.