A weird sound from.....

If you have a digital camera please take a picture of the wires, computer, desk and accessories. Something is picking up RF and have you tried moving the wires in the back around. Try isolating the power cords from the data cables from the speaker wires. Can you give me some details as to the system spec's, speakers. Have you a cell phone or wireless phone nearby ? Let's try moving wires and devices then go to the ferrite magnets.

Ok, my desktop (hp pavilion e9290f), the wires (they do not look like that messy, i took the picture from top ^^), speaker location, also I have phones and game devices on the desk, they have been like that for 2 years and nothing happened until a week ago, weird thing about this is that the sound pops up only in the morning around 9 am to 11 am or sometimes 12 after that it's normal again. Is my speaker fault or just I am unlucky???

Yeah, nothing odd going on from a wiring stand point. Can you think of any activity or person near by that coincides time wise with these noises. I wish I could look and say.....ah try this now. I know that from a pure stereo or home theater issue regarding wiring, you always keep all powercords together or as far from signal cords or interconnects. You can try this as well, trying to route the wires and even zip tie'g them so the cords are all tidy......this is a stretch. Then as I mentioned you can purchase some ferrites and wrap them around the lines.

Do you have a budget as I could make some suggestions? Are you gaming mostly, music, need deep bass or clear clean balanced sound?

Just two of many options !
http://www.amazon.com/Audioengine-A5...299238&sr=1-46

http://www.amazon.com/M-Audio-Studio...9299402&sr=1-2

Look around you neighborhood for a tall antenna attached to a building or a tower in some ones yard. A citizens band operator can cause this problem. I have heard these types of signals heard on a screen door when they transmit with to much power. That's no joke. If you live close to a port you could be picking up ships transmitting.

New speakers might not help, radio-waves travel better in the daytime than they do at night (or so I was once told by someone who knows a lot more about it than I do) which I didn't understand because I thought interference from the sun would be a factor.

I would wrap the room in lead !