If you are using GI for the extra lighting you should check the subdivision in those settings. And what goes for the Vray lights, well, try the same. Just pump up those subdivisions and see what happens. you might get way less noise. Also, have you set your enviorment lighting to white? If it's still black, it might cause noise aswell.
Also, If your scene is completely locked out of light entrances, try to use a backlight with a very dim lighting. so that the shadows don't appear.
Vray lights are much slower to render. It depends on the scene but you might be better off using standard lights with vray shadows.
With vray lights its all about the size of the light that determines the softness of the shadow. big lights have a big area. and area shadows are soft. The bigger they are the less defined the edges become. If you are using vray lights as john says up the subdivs on the light and you will get smoother results. something like 25 subdivs is usually enough.
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