Well just recently there is this really annoying intermittent noise coming from my radio. It does slightly vary with engine speed but not like you would normally think. I will try and get a recording of it if I can, but what would normally cause this?

bad antenna ground. or just a bad ground

OH forgot to mention, its ONLY when the engine is on. When off, its clear as a bell.

<== that sounds like thats ur problem

when your driving and you use your signal light you hear it click right. or accelerating you hear that too.

you are hearing alternator noise most likely.

Commonly caused by poor and/or dirty grounds. Check the interior ground as well as all the ground connections under the hood. Clean them.