I firmly believe deer hear an arrow coming in some instances and duck accordingly, not always but I have seen enough examples to verify this fact.
I took a shot at a huge doe as she walked under my tree and away from me. When she was about 6 yards away I turned it loose, the doe reacted by forming a "C" shape with her body, the arrow centered the C and missed I her completely. She didn't drop like one would expect from a normal deer, she dodged the path of the arrow.
Where I hunt deer are skittish, they always drop on a shot so you have to hold low. I took a shot at a deer on a food plot at a deer, food plot deer are really wired and will usually go into contortions when you loose and arrow at them. I feel like the doe I shot at heard the arrow coming and reacted accordingly, she froze and my broad head shaved a little hair off her brisket, right where I was aiming.
I was expecting her to drop into the arrow, she didn't and was probably the only deer I have ever shot at that froze at the shot.
I have seen other deer literally bounce their chest off the ground avoiding an arrow.