Dr. Oman Iman heads a team of scientists at Georgia Tech trying to give medicine better tools to prevent knee injuries by creating that maps out what a healthy knee should sound like—a sound that is so brutally painful, you very well might not get through it. Seriously, it's fascinatingly hard to listen to (Author's note: this could just be me, but hoo boy).

Amplified so that every part of the internal workings of the knee (bone and cartilage all rubbin' up on each other, to use the technical explanation) can be heard clearly, the result just sounds like pain. Unlike the cracking of wood or metal, there's something so inherently biological about the noise that your brain recoils instinctively. Knee injuries are one of the biggest risks in sports, though, so maybe it's worth enduring the medical equivalent of nails on a blackboard.

Sources: h/t Digg