I've always been very sensitive to high frequencies and have noticed a
ringing in my ears in the last few months (tinnitus).  It might be
caused or abetted by high frequencies emitted by my speakers and/or
monitor which emits a soft, high pitched whine from the back.  The
high frequencies from the speakers are caused by a poor designed amp
that powers them.  If I plug the speakers into my iMic (USB audio
adapter), instead of the audio out jack on the computer, its exactly
the same.  So I know its not the computer.  Its the amp.  There is a
subtle high frequency buzz that vanishes when the amp is turned off.  
Of course if I turn the volume down its still there as it is the
background noise from the amplification.  Its just not a low noise
design.

I'm wondering if anyone else has heard of this.  We sit so long and so
close to our computer speakers (my setup especially), any residual
irritations could mount up over weeks or months and manifest itself as
possibly tinnitus.  There seems to be no definitive treatment for
tinnitus in the medical field.