We at easyJet tend to describe the noise as the 'dogs barking in the hold', as it sounds more like dogs barking than a printer. The sound is very common on A319 aircraft.
The sound comes from the hydraulics and I believe that it happens either due to the way the hydraulics were shut down/started up (someone will no doubt correct me on that point!).
Some of the aircraft are noisier than others, but the noise does stop once you get into the air
