Researchers at Newcastle University used magnetic resonance imaging (MRI) scans to measure the response people had to sounds. They determined in 2012 the top five worst sounds in the world.
The first is a knife scraping against a glass bottle, and No. 5 is fingernails on a chalkboard. Listen to them all here.
1. Knife Scraping a Glass Bottle
2. Fork Scraping Against a Glass
3. Chalk on a Chalk Board
4. A Ruler on a Bottle