I have a Hitachi hard drive too, 7k1000.c, 1TB. I also hear that noise unfortunately, it's like the drive was seeking when it's in idle. I was talking about this on other forums, where other users have experienced the same noise, and have found no solution to it.
I've even written an e-mail to Hitachi, but they just told some general answer, as if there was something wrong with my hard drive. Clearly, it is not a problem, since many people have experienced the same and all of the driver are working just fine.
I wish Hitachi would tell us the reason for that noise.
Maybe storagereview could ask them so that they'd write a normal reply?