You might be able to experience it yourself. Just move your eyes all the way (ALL the way) to the right or left and hold them there for a second, you might hear/feel a high-pitched sensation almost like a slight tickle right where your eardrum is.
I wonder what other sensory anomalies we experience without realising ?
Also, eye saccades are a great example of this. If you look at your own eyes in the mirror and switch between looking at your left and right eyes, you don't see your eyes move. If you watch someone else do this, you do.
Sometimes when it's quiet and I'm laying down. I can feel vibrations, for many years I attributed them to subtle deep earthquakes or even perhaps the house or something shifting. But after having felt a similar vibration in many states. Many floors up or on outside ground. It's all quite similar. Although I've never had any formal meditation training, I have read and practiced it a lot before. I wonder if I'm feeling reality vibrating or perhaps at least in the sense the monks meant.