There might also be a technical problem on my side with this: The mic preamp & all the input sensitivity on every hardware & software control through the system is at absolute max gain to ensure that very quiet (<15 dBA/1m) sounds can be recorded and played back without the noise floor of the system (shhhhhhhhh) swamping out the quiet sound. A 60 dBA/1m input would probably translate to >80 dBA at 3". This may exceed the dynamic range of the system -- ie, it might overload the front end. Not sure, will have to try it. (You have to measure it at least 1/2 meter away, otherwise, the reading is inaccurate -- usually boosted in the lower mid/bass.)
I've given this problem some thought and can think of another possible solution.
Record pink noise at a non-clipping volume on your setup (let's assume this is maybe 40dB @ the distance from your microphone). Using programs like Wavegain and mp3gain, we can digitally (and losslessly) amplify the noise by a fixed amount to a value that can be measured (let's say it's amplified TO 60dB).
User takes the adjusted noise sample and sets the volume so that the noise sample is at 60dB. User now knows the accurate volume that this fan noise samples are at, since the unadjusted pink noise SHOULD playback at 40dB.
I guess this is a lot more effort than I initially thought. Are there any comments or suggestions to this?