Elite Bastards posted a preview on the Sapphire Radeon HD 3870 X2 Atomic WaterCooled

Connected to the board and water block is a unit which contains the pump, reservoir, radiator and a 120mm fan for cooling. This fan is connected to the graphics board itself to both power the fan and allow for temperature monitoring so that fan speed is automatically adjusted dependant on the heat being produced by the GPU. When idling at the Windows Vista desktop, this fan often doesn't need to spin up at all, and even when running graphically intensive titles at factory clock speeds we only ever saw it needing to run at its lowest fan speed. While the noise from this fan coupled with the water cooler's pump is certainly noticeable at all times, I'd hesitate to call it 'loud' per se, its volume level seems pretty acceptable for the average system to me, although you may disagree if you're looking to produce a near-silent high-end setup.

Sapphire Radeon HD 3870 X2 Atomic WaterCooled preview