Thanks for all the details about your new testbed, Eugene. Obviously a great system now even better.
There is only one disappointment for me: Acoustic measurement distance changed from 18mm to 3mm. I know this is to allow readings with an SLM that is not sensitive enough to go farther back, possibly in an environment that is not quiet enough. But such close distance is completely at odds with all known & accepted SPL measurement practices.
The main issue here is boundary / coupling effects which boost readings, particularly at the lower frequencies. You can hear this any morning while driving to work. The typical radio announcer/DJ speaks with his mouth close enough to the mic so that his voice is unnaturally chesty & deep sounding. This is caused by boundary / coupling effects. The very same effect applies to a mic placed so close to any noise source -- like a HDD. I hear it in audio recordings in my lab when HDDs and fans are placed too close to the mic.
An acoustics prof at the Univ of BC recommended I avoid getting any closer than about 1/2 meter when taking SPL measurements. (And also to stay at least a meter away from walls, especially corners where audio reflections reinforce each other.) Any closer, and the decibel reading cannot be trusted to be accurate. Taking noise measurements at 3mm would tend to compress the data range -- ie, the louder ones and quieter ones will both tend to be measured as louder, and the differences between them will tend to be smaller because all of them would have artificial boosts in the lower freq.
Any serious acoustics handbook will at least mention this issue of measurement distance. Here is one references on the web I found in a quick search:
MikeC, editor, silentpcreview.com