The sound I'm hearing (which I assume is coming from either one of my 2 hard drives), is a single, faint clicking sound followed by a very soft "hum" sound. It is distinctive and doesn't sound like normal hard drive operation. I've been hearing such a sound with about 4+ hard drives now, all WD Blues+1 black. Is this sound something that a drive would make when spinning down or using some power saving feature? That's the only thing I could think of, other than some type of physical damage, which seems unlikely because the drives perform well. On a laptop I had, I would get single clicks followed by another click right after. That series, I noticed, did affect the performance of the computer because there would be abrupt pauses until after that second click. Is there some way to test that my drives are healthy and performing up to spec?