A team of researchers from the University of Cologne and the University of Austria have discovered the reason why most of us shut our ears and contort our faces when we hear the sound of nails on a chalk board.
During the study, research participants were made to hear unpleasant as well as pleasant sounds, for instance the sound of nails on a chalkboard or a fork scraping a plate.
Some of the participants were warned about the sounds they were about to hear while the rest were told that they were to hear a piece of music.
Physical reactions of the participants like heart rate and blood pressure were recorded while they listened to the sounds. They were also asked to rate the sounds as pleasant or unpleasant.
The research showed that those who were informed earlier about the sound they were likely to hear rated the sound more positively as compared to those who were misled about the source of the sound.
Researchers are of the opinion that our response to these sounds could be part physiological and part psychological.
Researchers also said that the sound pitch which is between 2,000 and 4,000 hertz gets amplified due to the shape of the human ear canals.
Irrespective of how participants rated the sounds, most of them portrayed a higher heart rate and blood pressure when they were exposed to peculiar and unpleasant sounds.