Sounds can cause instantaneous reactions. For example, just about everyone instantly relaxes when they hear the sounds of crashing waves.  But when chalk scrapes a blackboard, just about everybody immediately cringes. And researchers wanted to find out why.

So, they had volunteers listen to recorded sounds while an MRI machine tracked their brain activity. The result: All of the sounds were processed in the part of the brain linked to hearing. But unpleasant sounds - like nails on a chalkboard, or a fork scraping across a plate - also activated the part of the brain that processes negative emotions. Which increased the intensity of the negative reaction.

But nails on a chalkboard is NOT the most annoying sound in the word. That honor goes to:
Whiiinniiinnng. You know, that high-pitched, protracted whining sound that children and even some dogs have perfected? That’s according to researchers from State University New York.

The researchers there asked people to do some basic math problems while they were listening to distracting and irritating sounds. They included a baby crying, a buzz saw, nagging, nails on a chalkboard and whining.

The results: The sound of whining was ranked worse than a buzz saw! Also, the volunteers made more mistakes on the math problems when they were listening to the whining than any other irritating sound. That’s because it was the hardest sound to ignore – which may be why children learn at an early age that whining can be an effective way of getting attention.