Static sound while trying to livestream

[ssulfur]

So I've been experiencing this really annoying thing while trying to livestream, and I somewhat hope that I'm not the only one that this has happened to.
When I'm recording, there is this static and annoying and loud sound that just won't end.
I'm not doing anything and before it worked just fine, but it's gone from bad to.... This!

I really don't know what to do, and if you want to know exactly what kind of sound I mean, just look at my latest (Portal2) recording. Help?!