Why we hate unpleasant sounds?

Brain imagining reveals that when exposed to unpleasant noise, amygdale modulates the response of the auditory cortex and heightens its activity, creating negative reaction.
There is a reason why you hate scratching sound-for example, of a knife on bottle or a fresh chalk on a blackboard-says a study by Newcastle University scientists.
The study in Journal of Neuroscience finds an interation between auditory cortex, the region of brain that process sound, and amygdale, which processes negative emotions.
Brain imagining reveals that when exposed to unpleasant noice, amygdale modulates the response of the auditory cortex and heightens its activity, creating 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 amygdale to the auditory cortex".
Also sounds in the frequency range of around 2,000 to 5,000Hz are found to be unpleasant. When exposed to such piercing sounds, amygdale modulates the auditory part of the brain creating unpleasant emotions. This dosn't happen with soothing sound of bubbling water.
"This is the frequency range where our ears are most sensitive. Although there's still much debate as to why our ears are most sensitive in this range, it does include sounds of screams which we find intrinsically unpleasant,"Dr Kumar says.
The study might help better understanding of the medical conditions of decreased sound tolerence of some people, which is known as hyperaucusis or misophonia (literally,"hatred of sound").
Next time, when you shy away from the scratching noice of an electric driller think about of Amygdale's hand behind it.