PeteG,
It's hard for me to compare it with an equivalent but I'd say at the lowest speed setting it is fairly quiet, put it this way I usually have some music playing when I'm working but I never have to turn it up above "normal" to drown out the noise of the AF. Even when I don't have any other background noise I don't tend to notice it.
I was in your position last year when it came to choose an AF and did consider the Microclene amongst other makes & models but what persuaded me towards the Record was not only the price but the ability to leave the unit running for a set time after you've left - I cant tell you enough what a really useful feature that is to have. It also has a remote control which is very handy too (as long as you remember where you've put it).
Alan