Anything to block out that noise! But why do unpleasant sounds affect us like this? For a new study , the researchers placed 13 subjects inside functional Magnetic Resonance Imaging fMRI machines, which measure brain activity by detecting changes in blood flow.
With this research, one hopes that the scourge of unpleasant sounds will finally be lifted from everyday life. I invision a future with noise-canceling devices in every classroom, office, and home that can protect us from the wretched range of frequencies that so disturb our fragile bodies. So what if that happens to the be the same range as speech? We can do this, people; we have the technology. Have a tip we should know? The team then asked Spanish volunteers to try to suppress their responses to grima.
This suggests grima is not a reflex reaction, but an emotional experience that can be influenced by thought, and is distinct from disgust. But although grima is most often associated with sounds, some participants said grima was triggered by the feel of certain objects — as foam rubber does for Schweiger.
Why fingernails on a blackboard stimulates such a strong aversive reaction is a mystery. A previous study, which earned an Ig Nobel Prize in , found that frequencies in the middle of the audio range were the most irritating, and these frequencies are very similar to the warning cries of chimpanzees. Those researchers speculated that our reactions to these sounds have their roots in predator-fleeing instincts from our evolutionary past.
The study's participants rated their discomfort to various unpleasant noises, such as a fork scraping against a plate or Styrofoam squeaking. The two sounds rated as the most unpleasant, they said, were fingernails scratching on a chalkboard and a piece of chalk running against slate.
The researchers then created variations of these two sounds by modifying certain frequency ranges, removing the harmonic portions or other concordant tones. They told half of the listeners the true source of the sounds, and the other half that the sounds came from pieces of contemporary music. Finally, they played back the new sounds for the participants, while monitoring certain indicators of stress, such as heart rate, blood pressure and the electrical conductivity of skin.
They found that the offensive sounds changed the listeners' skin conductivity significantly, showing that they really do cause a measureable, physical stress reaction. The most painful frequencies were not the highest or lowest, but instead those that were between 2, and 4, Hertz.
The human ear is most sensitive to sounds that fall in this frequency range, said study researcher Michael Oehler, a professor of media and music management at Macromedia University of Applied Sciences in Germany.
Oehler pointed out that the shape of the human ear canal may have evolved to amplify frequencies that are important for communication and survival. Thus, a painfully amplified chalkboard screech is just an unfortunate side effect of this mostly beneficial development.
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