Heightened activity between the emotional and auditory parts of the brain explains why the sound of chalk on a blackboard or a knife on a bottle is so unpleasant.
In a study in the Journal of Neuroscience, Newcastle University scientists reveal the interaction between the region of the brain that processes sound, the auditory cortex, and the amygdala, which is active in the processing of negative emotions when we hear unpleasant sounds.
Brain imaging has shown that when we hear an unpleasant noise, the amygdala modulates the response of the auditory cortex, heightening activity and provoking our negative reaction.
"It appears there is something very primitive kicking in," says Dr Sukhbinder Kumar, the paper's author from Newcastle University. "It's a possible distress signal from the amygdala to the auditory cortex."
Scientifically, a better understanding of the brain's reaction to noise could help our understanding of decreased sound tolerance such as hyperacusis, misophonia (literally a "hatred of sound") and autism, when there is sensitivity to noise.
MOST UNPLEASANT SOUNDS
Rating 74 sounds, people found the most unpleasant noises to be:
- Knife on a bottle
- Fork on a glass
- Chalk on a blackboard
- Ruler on a bottle
- Nails on a blackboard
- Female scream
- Anglegrinder
- Brakes on a cycle squealing
- Baby crying
- Electric drill
LEAST UNPLEASANT SOUNDS
- Applause
- Baby laughing
- Thunder
- Water flowing
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