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Human Ears Make Noise

Posted by timothy on from the buzz-more-when-nibbled dept.

KeelSpawn points to this article at Discover, which begins: "Until recently, scientists thought human ears were passive devices that detected and processed sounds, but new findings suggest that ears are like perpetually turned on stereo receivers that quiver spontaneously and sing along with incoming sounds."

2 of 34 comments (clear)

  1. Well, duh.... by Anonymous Coward · · Score: 5, Interesting

    The shape of the ears plays an important role, too. It alters the frequency response of noises heard so that you can spatially determine it's location.

    In simpler words, you can tell if a sound is above or below you. The little ridges and curves of your ear accent and muffle different frequencies in different ways. It's natural for you now, because as a child, you programmed your brain by looking for the source of the sound. Later on, you stopped looking at the sound source, and could tell where the noise was coming from.

    Take a cheap radio, and tune it to between stations, to generate some white-noise. Cover one ear, and move the speaker of the radio around above and below your uncovered ear. For extra fun, do it blindfolded, with a friend moving the radio around.

    You'll be surprised at how well your one ear can locate sound in 3D. If it was just receiving information like an omnidirectional antenna, then it shouldn't be able to process location.

    That's also why you can't determine where pure noises (like cell phones, smoke alarms, most electronic beeps, and some bird whistles) are coming from, or you have a hard time locating them. These tones do not have enough miscellaneous energy in multiple parts of the audio spectrum for the shape of your ear to fiddle with. The British are experimenting with new alarms that go "chuff", or that have white noise as part of the sound, to make it locatable.

    That's also why headphones sound so different (and unlocatable, spatially), because the headphones defeat the ear shape.

  2. Olds, not news by Red_Winestain · · Score: 5, Informative
    This is not new, it is old. The sounds produced by the ear are known as otoacoustic emissions. It is hard to tell from the lightweight Discover article what the new contribution from the researchers is, but the basic phenomenon is quite old and quite well understood.

    The best summary information on the web is the otoacoustic emissions web site. It has two lengthy reference sections, information on the use of otocacoustic emissions to test the hearing of new borns and infants, and lots more.

    Other information on this is easily obtainable by browsing back issues of the Journal of the Acoustical Society of America.