buzzing noise

If the sound comes from the system speaker, check for a hardware monitor in the BIOS. The system may be seeing an out of range voltage, temperature, or fan speed.

If it is coming out of speakers connected to your sound card, first check the power supply for the speakers, It may be bad.
Then check for driver updates for the sound card.

Answer 1 is a good place to start. Here are a couple other things to check.
Where are the cords connecting your sound card and speakers routed? If they run next to a power cord (or are bundled with it) for a long distance, you could be getting interference from the power cord.
Are the speakers right next to your monitor? If you have inexpensive or off-brand speakers, they may not be shielded well. Also if you have an older monitor it may not be well shielded. The same emissions that will eventually wipe a floppy left on top of a monitor could also be causing interference with your speakers.
Is the buzz ou hear constant (i.e. regardless of whether there is any other sound playing) or only in conjunction with other sounds? If the buzz is constant (and you've ruled out the possibilities put forth in Answer 1) I would suspect an interference issue. Try moving the speakers around to see if the buzz diminishes. Also try seperating your sound cord from any other power cords. Ifthe buzz onlu occurs in conjunction with other sounds, it could be any of a number of things: a bad connection at the sound card, bad speaker power supply, bad speakers, etc. You may only be able to solve your problem through trial and error.
I once had a problem where the power went out while the speakers were on. When the power came back, the power surge caused a tremendous feed-back loop (manifested by loud buzzing) in the sound system. The only way to clear it was to disconnect power totally from the speakers.
Hope trying one of these troubleshooting steps solves your problem.

I agree that it's an electronic feedback. If my cell phone is within 5 or 6 feet of my computer and a call comes in my computer speakers always buzz before my phone rings from the electronic signal the phone emits (I look at it as a kind of early warning system).

Bob.