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Why do we say some sounds are 'high' and others 'low'?

Ever wonder why some sounds are described as "high" and others "low," or why melodies are described as rising or falling?

Well, a team of cognitive scientists has, and they argued that humans are hard-wired to assign spatial positions to different types of noises.

In a paper published Monday in the journal PNAS, researchers in Germany found that people were more likely to identify high-pitched noises - think of a mosquito's buzz - as originating from elevated positions. Low-pitched noises, however - like the thud of a rock - were assumed to come from low elevations.

Researchers set out to test this spatial "mapping" in humans by exposing test subjects to a wide variety of sounds recorded in the German countryside.

The noises were played back through an array of speakers set up behind an opaque yet sound-permeable screen. Test subjects sat in front of the screen in a mechanical chair and were asked to point to where they thought the noise was coming from.

High-pitched noises usually caused the test subjects to point at a space that was head-height or higher, according to researchers.

But when the mechanical chair was rotated on its side, so that the listener was sitting at a 45-degree angle, or at 90-degree angle - parallel to the floor - the results were very different.

When the high-pitch noises were played back, people again pointed to an area above their head - but this time the "elevated" area was in an entirely different place. The area they pointed to was actually to the side of where they were seated in a normal position.

"We can only speculate about the origins of this mapping," wrote lead study author Cesare Parise, a researcher at the Max Planck Institute for Biological Cybernetics, and his colleagues.

"It could either be that at higher elevations, more energy is generated in high frequencies (e.g., leaves on the trees rustle in a higher frequency range than the footsteps on the floor), or it could also be that the absorption of the ground is frequency dependent in a way that it filters out more of the high-frequency spectrum."

The authors wrote that this spatial association is so ingrained that few people stop to think about it. Most cultures use the terms "high" and "low" to describe pitch, even when speaking different languages.

"Throughout the history of musical notation high notes have been represented high on the staff," authors wrote. "However, a comprehensive account for the origins of the spatial connotation of auditory pitch to date is still missing."

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