Motherboard booting help

[dsj]

When I start the power, there is a da sound coming out of the computer right before the clear beep that indicates a successful boot. Why is that sound there?

 

[dsj]

It's the frontal speaker. When I unplugged it there are no more of that sound. Sounds like the sound of the motherboard powering up and the speaker being connected. Like when you plugged a speaker and there is a puff sound. What do you people think?

 

[dsj]

any help?