The chirping sounds you're hearing is likely the air pump. The UV printers use a vacuum/pressure system to fill the subtanks and the sound you're hearing is it maintaining that pressure. Not an indicator of a leak or anything, as the vacuum system is pretty much on-demand, but the pressure system has a reservoir (white 1L bottle inside the machine). Since the pump uses a stepper motor bolted straight to the steel body of the machine, the noise is decently loud. On one machine I cut a small piece of rubber out and used it as a spacer to help dampen some of the noise.
The most common air pump is based on a NEMA 17 stepper motor, so you can also go all pro and look for a "NEMA 17 Vibration Damper" on ebay/amazon and get one to do it all fancy-like. Commonly found in copiers, since those damn things are packed with steppers and usually run in environments where silence is demanded a bit more than a noisy print shop.
