Sound Help

[Shockwave Pulsar]

About 6 months ago i bought a new computer, it's an hp pavillion.
Anyways it all seemed to work fine until i noticed a sound coming out of the speakers, needless to say quite annoying. the sound volume became louder when i increased the volume of the whole computer. so when i litsened mp3s or any kind of sound the annoying sound wouldn't let me hear the audio in peace... it was to loud, almost blocking the sound. and i'm a person who can be easily annoyed by that stuff... Hearing that sound in every song as background got quicly into my nerves.
One day i woke up and it was gone.
My problem it's thats now it's back and even louder. i just can't stand it anymore... if any one has any idea of what the problem could be, i would highly appreciate any help.

BTW: Sorry for any spelling mistake, english it's not my first lenguage.

[Endless]

The only similar situation I can think of is if you have the line-ins open. To check, go to your control panel, then sound properties, then mute everything like microphone and line-in until you find which one is causing the problem.

[Dr Unne]

Make sure you have the cable plugged into the right hole in your soundcard. On my old soundcard I could plug it into the wrong place and it'd still generate sound, but it sounded kind of like what yours does. Check all the other cables too. To your speakers and whatnot. Maybe try another set of speakers to make sure that it isn't just your speakers that're broken. Also, do you have a microphone plugged in? If so take it out and see if that helps. There are a lot of things to try. I can't think of any more.

[Shockwave Pulsar]

Wow, thanks Master Vivi and Dr Unne for your help! i was able to solve it!
Seems like Master Vivi was right, there was an especific hidden control in the sound panel that caused the annoying sound.