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Noise levels
The acoustic footprint of a hard drive has become one of its most important attributes—especially for PC enthusiasts who have built themselves near-silent systems. We're a little OCD here at TR, so we've constructed a Box 'o Silence to test the noise emitted by mechanical hard drives. This 18" x 20" anechoic chamber is lined with acoustic foam, and we suspend hard drives inside it, exactly 4" away from the tip of our TES-52 digital sound level meter. You can read more about the setup here.

To ensure the lowest possible ambient noise levels, we swapped the test system's graphics card for a passively cooled Gigabyte card and unplugged one of the Frio CPU cooler's dual fans. Noise levels were measured after one minute of idling at the Windows desktop and during an HD Tune seek test.

We've color-coded the results by manufacturer to make the graphs easier to read. Because they have no moving parts and are essentially silent, the SSDs are missing from the noise results. When they do appear in the graphs, the corresponding bars are greyed out to set apart what is really a different class of PC storage.

Although the NAS HDD is nearly as quiet as the Desktop HDD.15 at idle, it's much louder when seeking. In both cases, the WD Red 4TB is noticeably quieter. In fact, the WD drive makes less noise while seeking than the NAS HDD does at idle. You can definitely hear the difference between the two.

The NAS HDD's noise levels actually spiked as high as 38 decibels during our testing, likely due to excessive vibration. Our suspension system relies on elastic cords that hum audibly when the NAS HDD is hanging in the Box 'o Silence. The Desktop HDD.15 behaved similarly, so we used the same trick we employed to dampen that model's vibration. A paperback book was placed on top of the drive during our noise testing, adding enough weight to tension the suspension cords and reduce their oscillation. This approach eliminated chirping on the Desktop HDD.15, but it didn't eradicate the blips entirely on the NAS HDD.

Adding our paperback (Zen and the Art of Motorcycle Maintenance, if you're curious) only appears to affect vibration-induced noise. We tested the WD Black 4TB with and without the book in place, and that drive's noise levels were unchanged. I'm already contemplating a new mounting system for the Box 'o Silence—and a test to measure drive vibration.

Power consumption
Power consumption was tested under load with IOMeter's workstation access pattern chewing through 32 concurrent I/O requests. Idle power consumption was probed one minute after processing Windows 7's idle tasks on an empty desktop.

The NAS HDD's power consumption is identical to that of its desktop counterpart. The Red 4TB is more power-efficient at idle, but it draws more power under load. I wouldn't worry too much about such small gaps, though. Even if you multiply the deltas to account for five-drive arrays, the differences won't have a big impact on your monthly utility bill.