Does the sound of fingernails on a chalkboard Irks you?? WHY?

The shape of human ear and Bad Rap of sound, makes sound of fingernails on a chalkboard more irritating and stress enhancing – study
Many of us had experienced that the sound created while scratching finger nails on a chalkboards or chalk scraping on a chalkboard may annoyed you and sometimes mere thought of it can be enough to set some people on edge. WHY so?

The findings of a new study may explain it. Researchers explain that the shape of the human ear may amplify certain aspects of the sound of fingernails or chalk scraping on a chalkboard making it more irritating to the listener. The study also suggests that peoples’ perception of sound plays a role in deciding how irritating it is.During study some listeners rated the sounds as more pleasant if they were told they were listening selections of contemporary music rather than fingernails on a chalk board.
Researchers presented the results of their study this week at the annual meeting of the Acoustical Society of America in San Diego.

High Pitches Amplified by Ear Canal
It is found that fingernails scratching a chalkboard produces sounds at the peak of human hearing in the frequency range between 2000 and 4000 hertz
Researchers explain that the human ear is quite sensitive to sounds within this high pitch range and the reason behind it could be the anatomical shape of the ear canal that amplifies sounds at these frequencies, creating them reasonably louder to our ears.
Sounds with Bad Rap
however, when researchers removed pitch information in this range from recordings of fingernails scratching a chalkboard and played them to people, they rated the sounds as more pleasant.
Study
During study half of the participants were told they were listening to the sound of fingernails or bits of chalk on a chalkboard, and the other half was told they were listening to contemporary music. They were asked to rate the pleasantness or unpleasantness of the sounds. Meanwhile, researchers measured their stress responses, like blood pressure, heart rate and sweat.
Findings
People who knew that they were listening to fingernails on a chalkboard rated the sound as more unpleasant and had a stronger stress response, in particular sweating, than those who thought they were listening to music.
These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.

ref:http://www.setuhealthcare.com/