Is the TV signal part of the card activated? It might be turning off and on, increasing system strength of the sound because TV might need that, and the noise might be because it isn't finding a signal, or something.
I doubt since you've just installed the card, it'll be Itunes.
By any chance do you have on board sound? This will be affected more by cards of that nature being built to run off the CPU almost completly.
They aren't great for audio quality because of this, and you do get ALOT of interference.
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