I had a similar problem, my speakers gave a static and somewhat distorted sound.
My solution was to switch the data cable from cd/dvd drive from a 6gig/s to a 3gig/s along with the port I used (6gig to 3gig). I don't know why using a faster port and data cable created this feedback, especially with a cd/dvd drive, but it did. Who would have guessed.
My process, testing sound after every step:
1. Try different programs on your computer to see if the sound came out the same way. Example: WMP and Pandora
2. Try different speakers that you know work for other computers. Example: headphones and actual speaker system
3. Try different outputs. Example: Optical and audio ports
4. Disable any audio effects/revert them to defaults with your audio driver. Example: Default equalizer and environment.
5. Open you speaker properties and go to the enhancements tab and disable all sound effects.
6. In your speaker properties also, go to the levels tab and mute everything but the top most.
7. Lastly in your speaker properties try different sound qualities.
8. Uninstall and re-install the audio drive itself, requires the disk that came with the motherboard most likely. My system uses Realtek.
9. Check all cables to see if they are secure.
10. Move computer to a different location, maybe feedback is caused by something in the area.
11. Try use a different outlet for your power supply.
12. Try using an audio card if you can find one to borrow from someone because they don't come cheap.
13. Where the fun begins. Only use what is needed for you system. No Case, No Fans, No buttons/ports on the case itself. Use only what is necessary; the drive the OS is on, the motherboard, the graphics card. Plug in audio cable/mouse/keyboard into the MB obviously...If it is still giving static at this point, you know one of the things you are using is faulty (the motherboard, hard-drive, graphics card).
14. Place the motherboard back in the the case.
15. Add components to the system testing after each one is installed to see if the sound still works, starting with fans/case buttons/case ports because they are less likely to be causing the problem. Make sure you turn off your system while installing components even though it may be time consuming, you don't want to mess up anything else.
Step 15 is where I found my issue with the dvd/cd drive so don't give up hope.
-I know this is about a year later, but I hope this helps, this is my first post on any forum =)