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A research team at the University of Newcastle examined brain activity as subjects listed to 74 different sounds, from running water to a fork scraped over glass, to determine what sounds humans find most unpleasant.
Fingernails on a chalkboard, screeching tires and an animal crying are not as unpleasant to your ears as the sound of a knife sliding against a glass bottle, a new study finds.
A research team at the University of Newcastle examined brain activity as subjects listed to 74 different sounds, from running water to a fork scraped over glass, to determine what sounds humans find most unpleasant.
The sharp side of a knife on a bottle came out on top.
“Subjects were informed that they would be listening to unpleasant sounds in the MRI scanner but were not told about the type of unpleasant sounds or the overall aim of the study,” researchers said.
Scientists wanted to pinpoint how the ear transmits sound to the brain, that then codes that sound as unpleasant. They also needed to make these links separate from any emotional or cultural associations with a certain sound — like a baby crying or the sound of someone vomiting.
The most “dissociable” sounds had high frequencies, which is tough for the human ear to tolerate, the study concluded.
From here scientists were seeking to learn how the sounds — acoustics — affect the auditory cortex of the brain and also the amygdala, a primitive region that processes emotions.
The amygdala helps define the sounds as unpleasant, linking them to the physical and emotional reactions to sounds, like a high pitch wail, experts explain .
The reaction might also be there to alert humans to potential danger, the study found.
“For example, an animal cry (signaling the presence of a dangerous animal) may have different time and frequency domain structure related to the size of the animal.”
The results of the study were published in the Journal of Neuroscience.
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