I’m currently reading a fascinating book, “Annoying: The Science of What Bugs Us” by Joe Palca and Flora Lichtman. The two science journalists take a look at the literature in various disciplines (psychology, evolutionary biology, anthropology and others) to try to discover why certain things drive us crazy.
Of course, I was drawn to the chapter on annoying sounds, with no surprise that fingernails on a chalkboard clocked in as the number one annoyance as compared to others sounds. Various researchers have attempted to discover what it is about this particular sound that makes it so irritating. First, they filtered the high frequencies of the fingernail sound (their hypothesis was that high-pitched, “screechy” frequencies might be to blame). Surprisingly this only muffled the sound but did nothing to make it more pleasant. When they filtered the frequencies from 500Hz to 2000Hz, that did the trick.
A few reasons why this is important:
So the sound that we can detect at the greatest distance is a scream, and when the energy the human ear is most sensitive to is removed from the fingernail sound, it’s easier to ignore.
Another factor that may contribute to the fingernail sound being annoying is that it is more rough (a subjective perception of rapid amplitude modulation). Basically, the fingernail grabs the surface of the slate, and as you continue to move your hand down it’s stuck and then suddenly will slip and jump to the next position. This produces a highly unpredictable, varied sound. The roughness is what seems to make people cringe the most.
Just some things to think about next time you hear that annoying screech!