Two Plus Two Older Archives - Weird ringing with my 2405fpw

Lemme preface this by saying that I'm sorry if this has been discussed, but I have two minutes before I have to run and don't have time to do an adequate search.

I have a Dell 8400 and a 2001fp/2405fpw dual monitor setup. They both run at their max resolutions. When I had the 2001fp as the primary monitor and a secondary 17 inch LCD, I didn't have this problem: Sometimes when running Firefox on the 2405fpw, I get a weird very slight ringing; it's almost like background noise. When I load a different page, it goes away for a second, then comes back. The video display is bright and all connections seem to be solid.

Any advice?