Why Fingernails On a Chalkboard Sound Painful 176
sciencehabit writes "Some sounds are excruciating. Take fingernails squeaking on a chalkboard. The noise makes many people shudder, but researchers never knew exactly why. A new study finds that there are two factors at work: the knowledge of where the sound is coming from and the unfortunate design of our ear canals. 'The offending frequencies were in the range of 2000 to 4000 Hz. Removing those made the sounds much easier to listen to. Deleting the tonal parts of the sound entirely also made listeners perceive the sound as more pleasant, whereas removing other frequencies or the noisy, scraping parts of the sound made little difference.'"
Re:Just thinking about it (Score:4, Funny)
Re:My wife's voice (Score:5, Funny)
Yeah, inflatable plastic makes a balloon-like squeal when punctured.
A little late on this one (Score:4, Funny)
You don't need an audiology experiment to figure this out. Harvey Fletcher and W. A. Munson established the lab work back in 1933, resulting in the Fletcher-Munson Curve [slashdot.org] which illustrates how the sensitivity of the human ear varies at different frequency ranges and volume levels, and is most sensitive in the 2-6kHz range. It's fair to assume this range is more sensitive since it is the hardest range for predators to keep silent while stalking prey, i.e. a twig snapping.
It is believed mankind has pre-historic rodents to thank for their advanced auditory system, which developed during the 65 million year period where mammals and dinosaurs co-existed. During this time there was low oxygen content in the air, so mammals had to maintain high respiratory rates, making them easy prey for the much larger dinosaurs, whose respiratory system involved hollow bones to transport air directly throughout their bodies rather than just lungs to deliver oxygen to the bloodstream. (Birds benefited from the hollow bones to fly, but only use lungs for respiration now that oxygen levels are up.) Mammals had to forage at night and depended almost entirely on their auditory systems for defense. 65 million years of that is likely the only reason we can discern music, much less appreciate it.
As a sound engineer I can attest that the 2-6kHz range is of special significance when putting a mix together. It's usually actually more important that the 2-6kHz range of each voice or instrument be balanced against each other than each voice or instrument be of even frequency response themselves. If something is dominant in that range, it dominates the listener's attention every time. If something has a sharp spike in that range, meaning a very narrow frequency band, it will not be pleasant to the ear. If you check out the frequency response graphs of the cheaper guitar speakers by clicking on the options here [usspeaker.com], you might notice they all have spikes around 2-2.5kHz. That is why they suck.