Late in 2014 I had cause to undergo magnetic resonance imaging of my head as a diagnostic procedure. If you've never had one before, this procedure can involve a head x-ray (to make sure you don't have any ferrous material in tender places that might get ripped out by a very powerful magnetic field). It definitely does involve an hour or two laying on your back on a backboard with snug straps holding you in place (because if you move it'll mess up the imaging data) while you're stuffed into a relatively small tube in the core of the MRI machine. This meant that I had a couple of hours to enjoy the unusual sounds that MRI machines make when they're in full operation with someone inside. I'll admit, after the first hour or so I decided to take a nap and wait the rest of the procedure out, but while I was awake I made a point of memorizing what the sounds looked like.
The image beneath the cut is what a sequence of sounds near the beginning of the process looked like. The broad color bars on the left-hand side were some sort of deep thrumming or groaning sound on my left-hand side. The double vertical line of yellow blocks was a stacatto knocking sound that seemed to trace my head on my right-hand side from crown to neck. It also felt like my right hand was vibrating violently, like it was being shaken up and down.
This is only an approximation - I'm no artist so this is the best I can do. The background's black because I had my eyes closed.