Check out this silent video above. Are you hearing a thumping noise in your head from the bouncing structure hitting the ground? If you are, this is due to a form of synesthesia; a systematic and involuntary sensory experience induced by an unrelated stimuli. Since we are expecting to hear a sound from a large structure hitting the ground, our brain is creating the feeling of hearing a sound that is not actually there. After watching a few times over, you can feel the pressure in your head and even experience your ears ringing!