Sound of fingernails scraping chalkboard

The sound of fingernails scraping chalkboard is a noise produced when fingernails are dragged across a chalkboard, producing vibration. The noise is often considered one of the most unpleasant sounds. Its effect was famously demonstrated in a scene from the film "Jaws", where Robert Shaw's character brings a noisy room to silence with a long scrape across a blackboard. [cite web|url=http://www.filmsite.org/scenes21.htm|title=Greatest Film Moments and Scenes]

Why it repulses humans

It has been suggestedwhom that people's aversion to the sound is because it sounds like the warning call of a primate ancestor. However, a study using Cottontop Tamarins, a kind of New World Monkey, found that they react similarly to both screeching sounds similar to fingernails on chalkboard, and to amplitude-matched white noise. This is different from how humans react, as humans are less averse to the white noise than to scraping.cite news|publisher=Vancouver Sun|date=2005-11-14|page=A6|author=Roger Highfield|title=Study seeks root of noises that annoy us]

A 1986 study attempted to determine why the sound was so unpleasant. It used a tape-recording of a three-pronged garden tool similar to a fork being "" across a chalkboard, which reproduces the sound of fingernails on chalkboard. It also used other sounds for comparison. They then manipulated the recording to remove the lowest, highest, and middle pitches. The results were then played back. It was determined that the middle pitches are what make the sound of fingernails scraping chalkboard so bad, not the highest ones as previously thought. The authors hypothesized that it might be due to predation early in human evolution; the sound bore some resemblences to the alarm call of macaque monkeys, or it may have been similar to the call of some predator.cite web|url=http://www.psychonomic.org/search/view.cgi?id=11185|title=Psychoacoustics of a chilling sound|work=Perception and Psychophysics|pages=77-80|publisher=Psychonomic Society|year=1986|author=Lynn Halpern, Randolph Blake, & James Hillenbrand|format=PDF] This research won one of the authors, Randolph Blake, an Ig Nobel Prize in 2006.cite web|url=http://www.physorg.com/news79531741.html|title=Fingernails on a Chalkboard Garner Psychologist Ig Nobel Prize|date=2006-10-08|accessdate=2008-04-09] More recent research contradicts this hypothesis. [citation|journal=Applied Acoustics|title=Scraping sounds and disgusting noises|author=Trevor J. Cox|year=2008|url=http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V1S-4RJ4KPP-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=ac5160ddc21306e1b5382c4ec3b41b88]

Is it really the worst sound?

A study was conducted by Trevor Cox, a scientist at the University of Salford, to determine the most repulsive sound in the world.cite news|title=FYI|publisher=Popular Mechanics|month=May|year=2007|page=102|author=Brandon Miller & Fred Koschmann] It involved uploading clips of 34 sounds onto the website sound101.org and having people from around the world rate them.cite web |url=http://www.sound101.org/aboutIntro.php |title=About Bad Vibes |accessdate=2008-04-06 |last=Cox |first=Trevor |authorlink= |coauthors= |date= |year= |month= |format= |work=Bad Vibes Website |publisher=Salford University’s Acoustic Research Centre |pages= |language= |doi= |archiveurl= |archivedate= |quote= ]

Fingernails scraping chalkboard was not the worst sound, only coming in 16th place. The worst sound was that of someone vomiting, followed by microphone feedback, babies crying, and a miscellaneous "scrapping (sic) sound".

Although the results are thought to be influenced by culture, Cox felt that the disgust reaction to certain sounds was evolutionary in nature. The disgust reaction to disease probably evolved to avoid getting sick. Females were in general more disgusted than males; it is speculated that this is due to females not only preventing themselves from getting sick, but also their offspring. In all, females rated more sounds worse than males, although the sound of a baby crying was a notable exception. Disgust also decreased with age.

References

External links

* [http://www.sound101.org/ Sound101 Bad Vibes]
* [http://www.straightdope.com/classics/a2_317b.html The Straight Dope: Why is the sound of fingernails scraping a blackboard so annoying?]