system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why is scratching on a chalk board so universally horrid sounding?
gpt
The frequency of the sound is in a range that irritates the human ear. Sort of like a dog whistle to a dog. Read an article about this. Scientists tested the frequency of the noise and have a better explanation maybe. "The most painful frequencies were not the highest or lowest, but instead were those that were between 2,000 and 4,000 Hz. The human ear is most sensitive to sounds that fall in this frequency range, said Michael Oehler, professor of media and music management at the University of Cologne in Germany, who was one of the researchers in the study.Oehler points out that many acoustic features of human speech, as well as the sound of a crying baby, fall in this frequency band, suggesting that the shape of our ear canal may have evolved to amplify frequencies that are important for communication. Having these frequencies amplified could have been advantageous for survival, allowing people to come to the rescue of their screaming infants quicker, and thus improve their  offspring's chance of survival, or coordinate more effectively during a hunt. In this scenario, a painfully amplified chalkboard screech is just an unfortunate side effect of this (mostly) beneficial development."