- This is a misuse of radio button control where (by convention) there always should be one (and only one) selected item.
- Unselecting all items is not noisy (IMO) and recall same pattern used in other controls (for example combo boxes) where no selection means multiple selection. This is a benefit but it's also a drawback (the same you have for combos): it's almost impossible to have a no selection state (for example to distinguish a state where user didn't select anything); to avoid this you may consider what the other answerother answer says. Note that this is a bad usage for radio buttons, if it's what you need then you should use another control.
The other answers address radio button issues (one of themone of them even attempting to unify checkbox and radio visual model). It's a model already in use on some OSX applications and default Gnome theme then it won't astonish many users (with visual style variations it's in use from 1980s in Motif widget toolkit).