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Human Ears Make Noise
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."
Quick, hand me that screwdriver!
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.
No wonder I can't get Santana's Smooth out of my head. My damn ears are singling along!
Believe nothing -- Buddha
[vaguely off-topic:]
:)
I first read of something like this nearly 20 years ago. When Pink Floyd's _The Final Cut_ came out, it utilized something called "Holophonics," the creation of some guy named Zuccarelli (or somesuch). The basis of his system was that the ear produces continuous high-pitched sounds, and the sounds we hear in everyday life interfere with those sounds, and are processed by the brain to produce a 3-D soundscape.
He then went on to assert that, by combining sound effects artificially mixed with that same high-frequency pitch, they can create and record that "interference pattern," much like a visual hologram works. Then, by playing that pattern back to the user (with nicely spaced speakers or, especially, wearing headphones), they could recreate the soundscape perfectly.
On the plus side, it worked. I heard a broadcast of a Roger Waters concert, where he demonstrated walking behind the listener and striking a timpani. Sounded cool.
On the minus side, it was a load of crap. The technical issues are just way too numerous to go into here, but the bottom line is that it was probably nothing more than nicely-recorded binaural sound. No new discoveries there.
[Returning to topic]
But, still, there was that case of the sound being produced by the ear -- at about the same time as holophonics coming out, I read some articles that sounded much like the current article -- there's sound, it's unpredictable, and we're not sure why it's there. Sounds like they're starting to figure out why.
Of course, anyone who listens to Suzanne Vega would have known all this years ago -- "Blood makes noise / It's a ringing in my ear."
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.
I can't help but wonder what that sound is like. It would be interesting to have someone actually point it out to us.
On a slightly unrelated note, I hope that they can make use of this knowledge to put an end to the ringing in my ears.
testing out my trending skills
When making sounds, the materials near the sounds resonate in tune with the sound!
On a serious note, does this all mean that those who use cotton swabs to clean out the ear canal are actually damaging their hearing because they may be damaging the hairs?
testing out my trending skills
Another noise that is hard to locate are sirens of emergency vehicles. This is why some countries (Britain, I believe) now use emergency vehicles that emit white noise and a regular siren sound, so other people on the road can more easily tell where the vehicle is coming from.
have you ever put your hands over your ears and heard that humm?
This makes sense, in the same way that small current loops used to measure magnetic field cause very small disturbances in the overall field. The whole assembly of currents, fields have to be a consistent solution of Maxwell's equations.
It gets me to thinking, though, that our audio language is probably not completely optimized yet, in terms of maximizing information flow.
That is, if you were to transmit maximum information in bits/second over the same frequency range as the human ear is capable of processing, it's probably a lot more than the fastest intelligible human speech (~400 words per minute).
"Provided by the management for your protection."
"Most hearing loss in old age is caused by the death of the hair cells, which are not regenerated."
Hearing loss with aging is unnatural. Hearing loss in the elderly is not common in primitive societies. We assume it is a normal part of aging because we are exposed to so much noise, but in fact it is not. In many non-industrial societies, older people hear quite well.
Hearing loss is caused by death of the hair cells, but that death in turn is caused by overdriving them with excess energy, that is, loud high-amplitude sounds.
70 decibels is a normal conversation, 80 decibels is damaging over time, and city noise is commonly louder than 80 dB. You probably listen to your music louder than that, too. Concerts? Wear earplugs, or you'll probably have demonstrably worse hearing afterwards. Any sound that makes your ears ring is probably damaging.
Ontopic: The idea that the ears are active, and produce sound is not at all new, although the demonstration that those sounds are externally audible is surprising. The very statement that doctors are listening to those sounds to check the health of infant hearing, tells you that this isn't brand new research.
Assembly is the reverse of disassembly.
The idea that the ear is a self-tuned oscillator with positive feedback was proposed as far back as 1948, in a paper by Gold (Proceedings of the Royal Society, London, volume B 136, page 492). It wasn't taken seriously back then and there was no evidence, but the evidence -- and more theoretical support and models -- came starting around 1998, in work by Hudspeth (Rockefeller Univ, NY) and others. Since then there have been plenty of papers; it's more than a "few months" old...
It gets me to thinking, though, that our audio language is probably not completely optimized yet, in terms of maximizing information flow. That is, if you were to transmit maximum information in bits/second over the same frequency range as the human ear is capable of processing, it's probably a lot more than the fastest intelligible human speech (~400 words per minute).
Add a little noise to the equation, and you'll see why human language is so close to optimal. It has language that let the ear separate it from ambient noise. It's optimized for use in the wild, not the lab.
Will I retire or break 10K?
(subject says it all :)
Liberty uber alles.
that's old was known in 1977 see -b iop hys_atu.html
http://www.physics.purdue.edu/deptinfo/postlh/
Interesting concept, I wonder if that is how we can "feel" the presence of another person in a room without actually seeing that person first. I dont know how many of you have had that experience. That could be one way of describing it...
OK,
- B
http://www.bradheintz.com/
- updated
One way is by smell. Your subconscious could be aware of the scent of someone.
;).
Another is by hearing. Get someone to put a hand in front of your ear and you can tell there's something there. So if you subconsciously know how a room sounds, if something big enough is in the room and alters the baseline soundscape you could notice. I guess bats/dolphins are much better at it, and they make noises to help too.
I suppose some people's ears make enough noise for them not to have to chirp like a bat
Cheerio,
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