Noise levels
Noise levels were measured with an Extech 407727 Digital Sound Level meter 1" from the side of the drives at idle and under an HD Tach seek load. Drives were run with the PCB facing up.

Despite spinning at a full 7,200RPM, the 640GB Caviar SE16 matches the Caviar GP for the lowest seek noise levels we've seen from a 3.5" hard drive. Idle noise levels still favor the GreenPower drive, but only by a fraction of a decibel.

Power consumption
For our power consumption tests, we measured the voltage drop across a 0.1-ohm resistor placed in line with the 5V and 12V lines connected to each drive. Through the magic of Ohm's Law, we were able to calculate the power draw from each voltage rail and add them together for the total power draw of the drive.

With only two platters to spin, the 640GB Caviar has remarkably low power consumption both at idle and under a seek load. Western Digital's GreenPower drives are more energy-efficient, of course, but with the exception of a single-platter 160GB Barracuda at idle, they're the only ones that are.