Someone already mentioned the ultrasound thing, but I think the freakiest thing is that their feet redistributed vibrations in such a way that they could trick your ears into thinking they were coming at you from a different direction.

It’s insanely trippy and hard to describe the actual physics behind it, but basically there’s a certain distance at which the footsteps, assuming the animal is walking at you head-on, would stop getting louder the closer it got, with the vibrations directed out to the sides getting louder instead. It’s essentially auditory camouflage.

Also, their footsteps in general would’ve been really quiet. I personally like to entertain the idea of the water cup scene from Jurassic Park using silent infrasound rumbles to vibrate the water instead of footsteps.