Airline is cheap, mount it a billion miles away in a shed!
The way you mount it is important, obviously they have rubber feet but if the airline is touching something it can vibrate through that, also I find that putting them inside cabinets (specially small sections) can sometimes make them resonate slightly louder.
Maybe use some sound proofing in the cabinet, or wrapping the air pump up in some (eggcrate)foam, yes this will make it warmer but they're so cheap I wouldn't worry.
Timer turning it off at night? or even just off during the times you often go to sleep turning it on at a rough guess when you have normally fallen asleep.
I like the running water (and bubbles) whilst sleeping, soothing.