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 tested with the PCB facing down to accommodate the ATA adapter.

Spindle speed is a big factor in our noise level tests, as fewer RPMs generate less noise at both idle and under a seek load. Surprisingly, though, the 4,200-RPM MHV2040AT isn't the quietest drive of the lot. That honor just barely belongs to the Momentus 5400.3.

Looking at our 7,200-RPM drives, the Momentus 7200.1 is a little quieter, especially under load, than the Travelstar 7K100.

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. Since mobile drives only tap the 5V line, their 12V power draw was zero.

Less than one watt separates our mobile ATA drives both at idle and under a seek load, but interestingly, our 2.5" Serial ATA drive proves to be even more power-hungry. The most impressive result here has to be the Momentus 5400.3, which actually manages to consume less power under load than even our 4,200-RPM MHV2040AT. Seagate's Momentus 7200.1 also consumes less power than the Travelstar 7K100 under load, but not at idle, where the Hitachi drive has a 0.2 W advantage.