"Phantom" Audio/Bass..??

Hello

I have an extremely bizarre problem.

I recently bought an eMachine with onboard RealTek HD sound...

I'm running Vista Home Premium.

Even with speakers unplugged, and audio devices muted/disabled;
My computer insists on making low bass type noises when I game.

Even with the game sound options off, and the built in monitor speakers' audio feed cables never plugged in.

Is it possible that I am getting some kind of feedback? I do have a Klipsch 5.1 woofer under my computer desk, but I even pulled its power cord.

These noises are so annoying and bass oriented, I can't use my computer late at night (I live in an apartment with sound curfews), and there are no speakers/output devices plugged into ANY jack at all!

Is it possible to get feedback like this perhaps from my monitor's built in speakers? This problem is driving me berserk!

Thanks in advance for any ideas or theories.
>_@
-Seif

 

AMD 64 DUAL CORE 3.17
nVIDIA 6400 ONBOard
3 Gigs DDR3 ram
Vista home premier with all updates
Hannspree 2440x1680 LCD with a video and audio jack