The fingernails scratching the chalkboard produce sound in the frequency range between 2000 and 4000 hertz. Human ear is more sensitive to sounds in this pitch range. Moreover, the anatomy of ear canal amplifies the sounds in this frequency range, making it even louder to the ear. This was clear as people rated the same sound, fingernails scratching a chalkboard, as more pleasant after the pitch information was altered.
Professor of media and music management at the University of Cologne in Germany, Michael Oehler was one of the researchers. He said that it was known beforehand that frequency at the top range of human hearing play a major role in making a sound pleasant or unpleasant. This research was helpful in determining the exact range of frequency at which unpleasantness sets in.
Moreover, half the people participating in the study who were told that they were listening to contemporary music, showed more tolerance for the sound. Their stress level was also found to better as indicated by blood pressure, heart rate and sweat. These findings and research are yet to undergo the peer review process after which the can be published in a medical journal.
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