Cringing At The Sound Of Fingernails Scraping The Chalkboard? Science Explains Why

Everyone just cringes at the screeching sound of fingernails scraping on a chalkboard. There’s no surprise there that the sound it makes is unpleasant to the ears but no one even bothered to wonder why. But for Michael Oehler, a musicologist from the Macromedia University for Media and Communication and Christoph Reuter, also a musicologist from the University of Vienna, there is a need to know the reason for such reaction and it all boils down to human anatomy and psychology.

The latest study by Oehler and Reuter involved using other sounds that elicit the same reaction as the sound made by scraping on a chalkboard, such as styrofoam squeaking and a fork scraping on a plate. Some of the subjects know where the sound is coming from while others were told that they are listening to a musical composition. The participants were then asked to identify the worst sound they have heard. At the same time, the researchers monitored heart rate, an electrical conductivity of skin and blood pressure to see signs of distress.

The study found that unpleasant sounds like fingernails screeching on a chalkboard can cause a physical reaction.

The study found that unpleasant sounds like fingernails screeching on a chalkboard can cause a physical reaction; there were significant changes in skin conductivity. In addition, the frequencies of those unpleasant sounds are within the frequency range of human speech, which is between 2,000 and 4,000 Hz. Eliminating the frequencies make the sounds easier to listen to but eliminating the noisy, distinct scraping sound did not make a difference.

Psychology also played a role in the study. Participants who knew that the sound came from fingernails scraping the chalkboard rated the sound as more unpleasant compared to if they believed the sound was part of a musical composition. Despite thinking that the unpleasant sound came from a musical piece, the skin conductivity still changed, which only means that the physical response remained.

According to researchers, the shape of the ear canal could be responsible for the retained physical reaction

According to researchers, the shape of the ear canal could be responsible for the retained physical reaction. Previous studies exhibited that the shape likely amplified the frequencies between 2,000 and 4,000 Hz. Scraping your fingernails on the chalkboard results to an amplified sound that can be painful to the ears.

Source: Wired