Out of 74 sounds, volunteers rated the five most unpleasant as:
1. Knife on a bottle
2. Fork on a glass
3. Chalk on a blackboard
4. Ruler on a bottle
5. Nails on a blackboard
ALSO: Why nails scraping down a blackboard is such an unpleasant sound
Scientists say our reaction to the sound of scraping nails – which is in the same frequency range as screams and babies’ cries – could be an ancient survival instinct. The study scanned the brains of 13 volunteers while they listened to a range of sounds before rating how much they liked them. The more unpleasant a sound, the greater an almond-shaped brain region known as the 'amygdala' lit up.
It then activated the auditory cortex, which processes sound, leading the volunteers to perceive the noise more keenly.
