In order to be able to get a noise level for each drive, we built a special crate, lined up with panels of quietizing material. It is 50x50x40 centimeters in size and can also be used for other devices as well (fans, CDROM drives etc).
That's a photo of our noise measurement crate. We make use of a little digital analyser from a German mail-order company to get a dB(A) value. Let me please make clear that this method is absolutely proprietary, and therefore our results cannot be compared with results of other reviews.
In the middle you can see our high fidelity microphone from Sennheiser inside the metal pipe. Directly below is the place where the device will be put. The surface is covered with a special rubber (the black pad), which is able to absorb all kinds of vibrations, so we can be sure that the only noise inside this crate comes from the drive itself.