Do you want to disable the annoying startup sound in Windows 7? Here’s how to quickly do it.
Open Start Menu and go to Control Panel.

Click on Hardware and Sound.

Under Sound Options, click on Change System Sounds.

From the Sounds Settings window, uncheck Play Window Startup sound as shown in the screenshot below and click OK.

If you want to enable it again, follow the same steps. Then check the Windows Startup Sound option.
To get to the sound settings without clicking through the UIa, click Start and type: sound options then click Enter.

Then click the Sounds tab and uncheck Play Windows Startup Sound and click OK.

While the Vista and Windows 7 startup sound isn’t as annoying as XP, but you can still turn it off.

Anyway of doing that to for the Mac?
Hope you find your answer at this link:-
https://discussions.apple.com/thread/2062133?start=0&tstart=0
Is there a way for it to make the sound when it is actually ready to use? What is it there for if I still have to wait to start new programs?