Previously, scientists have speculated that we might found these sorts of high-pitched sounds so irritating because they acoustically resemble the alarm calls of our primate relatives, such as chimpanzees. “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.” Why would the amygdala activate specifically for sounds within this range? “It appears there is something very primitive kicking in,” says Sukhbinder Kumar, the paper’s lead author, from Newcastle University in England. The researchers found that the amygdala interacted with signals coming from the auditory cortex, increasing the amount of unpleasantness conveyed by sounds at the top of the list, which all happen to occur in the frequency range between 2,000 and 5,000 Hz.īrain activity in the amygdala increased for unpleasant sounds. The MRI scans revealed that along with the auditory cortex (which processes sounds), activity in the amygdala-the region of the brain responsible for producing emotions-increased in direct proportion to the perceived unpleasantness of the sound. Here were the four they rated as the least irritating:Įven more interesting than the rankings were the parts of the brain that lit up with activity when the research participants heard the irritating noises. They also played the participants a number of more pleasant noises. Their top ten most irritating sounds, with links to audio files for the worst five (although we can’t imagine why you’d want to listen): As part of their research, published last week in the Journal of Neuroscience, they put 16 participants in an MRI machine, played them a range of 74 different sounds and asked them to rate which were most annoying. When it comes to noises that bother everyone’s ears, it’s seemingly a given that scraping fingernails across a slate board is the one that everyone hates most.īut when a group of neuroscientists decided to test which sounds most upset the human brain, they discovered that fingernails on a chalkboard isn’t number one. It’s so universal that it’s become a cliché: nails on a chalkboard. A new study examines which sounds are most unpleasant to the human ear.
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