You have visited SilentPCReview, haven't You?
There are few issues when doing noise measurements.
- You need a very good (=sensitive) SLM (sound level meter). SR measures the noise from a distance of 18 mm, which is done because their meter is a basic one (which most likely cannot register lower than 25-30 dBA). The meter used at SPCR is actually borrowed from University of British Columbia, and is rather expensive.
- The environment & rest of the computer need to be very quiet. If You have read the articles here, You've seen comments like "While one may argue that differences below, say, 43 dB/A or so get lost in the noise generated by other parts of the system (or even general ambient noise, for that matter)" (from SP1614C review) basically mean that the reviewer's system was masking the noise created by the drive.
Improving (or even changing) the testing methods would also mean that the comparison between existing results and new results would be difficult, if not impossible.
Well, keeping in mind that Eugene asked about suitable motherboards for Testbed IV a while ago, testing methologies could also be changed in the process...