Thank you -- the info was in SPCR's "archives" all the time!
Without the fan monitor cable plugged in, the rear fan does not spin at all when the temperature is low. This is excellent for silencers. It means that the only source of noise is the intake fan in the middle of the case, away from any direct paths to the user's ears. It also spins slowly enough that it is probably close to or below the ambient noise level in most rooms, effectively making it silent in a low power system. The low-profile intake fan is quite well-behaved, even at the relatively high starting voltage of 5.3V.