I think the reason a "tick" isn't next to the Noise Reduction setting when selected is because there are various different modes of the Noise Reduction because in some games I have to choose the Noise Reduction option more than once to clear up the crackling.
I have now assigned the option to the
N key.
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Intel C2D E4500 @ 3.6GHz
Asus P5N-E SLI
Point of View 8800GT OC
4GB Corsair XMS2 PC2-6400C5 DDR2 SDRAM
Windows Vista x64 Ultimate SP1