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MirjamVonk

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People Hear with Their Skin, As Well As Their Ears

 

http://www.scientificamerican.com/article.cfm?id=skin-hearing-airflow-puff-sound-perception

 

 

A new study shows that the skin could help us hear by 'feeling' sounds

 

 

The act of hearing is a group effort for the human body's organs, involving the ears, the eyes and also, according to the results of a new study, the skin.



In 1976 scientists discovered the importance of the eyes to our sense of hearing by demonstrating that the eyes could fool the ears in a peculiar phenomenon named the McGurk effect. When participants watched a video in which a person was saying "ga" but the audio was playing "ba," people thought they heard a completely different sound—"da." Now, by mixing audio with the tactile sense of airflow, researchers have found that our perception of certain sounds relies, in part, on being able to feel these sounds. The study was published November 26 in Nature.



Normally when we say words with the letters "p," "t" and "k," we produce a puff of air. This puff helps the listener distinguish words with these letters from those with the similar sounding "b," "d" and "g," respectively, even though the puff is so subtle that most of us do not even notice feeling it. "Unless you're a microphone manufacturer or a radio jockey or a phonetician, this isn't something that you're aware of," says Bryan Gick, an associate professor of linguistics at the University of British Columbia in Vancouver, and lead author of the study. Donald Derrick, a graduate student in the University's Department of Linguistics, is the other author on the study.



Gick and Derrick set out to determine if these puffs of air help us to perceive "p" and "t" sounds. The pair had 66 participants listen to sessions of recorded sounds through headphones. In one session, the participants heard a combination of "pa" and "ba," and, in the other, "ta" and "da."



The researchers also sent light bursts of air from thin tubes placed over participants' skin, over either their hand, neck or in their ear. The participants were blindfolded so they did not know where the tube was placed. In some cases, puffs were released with the appropriate sounds, "pa" and "ta," and in other cases, they coincided inappropriately with "ba" and "da." As Gick notes, the puffs were about half as forceful as what we would feel in a normal conversation, and most participants were not even aware of them over the course of the experiment.



The researchers found that if there was no air puff, participants misheard "pa" for "ba" and "ta" for "da" 30 to 40 percent of the time. The accuracy improved 10 to 20 percent when an air puff over the hand or neck accompanied "pa" and "ta." No improvement occurred, however, if an air puff was sent through the tube in the ear, suggesting that the participants were not simply hearing the airflow.


The opposite effect was observed when the participants received an air puff with the inappropriate sounds— "ba" and "da." While subjects correctly identified these sounds in about 80 percent of cases when played without the release of air, the accuracy decreased by about 10 percent if the sounds were accompanied by puffs of air. 



"Largely, in English, the difference between 'pa' and 'ba' is this puff of air," Gick says.


The ability of the skin to contribute to hearing could be due to the fact that the largest organ in the body is covered in mechanoreceptors. Gick says that he has even found that air puffs sent to the ankle can help the listener comprehend those "p," "t" and "k" sounds. These receptors in skin cells, which are similar to the ones in the ears, respond to the pressure created by airflow.



In the real world, the cues available to a listener vary. Standing a foot or closer to someone speaking normally should produce tactile puffs, Gick says. However, if the conversation were taking place on a windy street, this sensory input would be destroyed. Although people can hear sounds in the absence of airflow, these sensory cues could make it easier to distinguish between two words, such as "tall" and "doll," especially if there is a lot of ambient noise. 



The feel of sounds could be exploited in devices for groups such as the hearing impaired. Gick is in the early stages of exploring how to incorporate into hearing aids airflow-detecting sensors that would produce a synthetic puff to the side of the neck. Because the skin mechanoreceptors among the hearing impaired typically function normally, Gick says, this additional tactile stimulus could help the person wearing the device perceive sounds. A similar concept could aid pilots in their noisy work environments.

 

 

Love, Mirjam


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Mirjam Vonk
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cbBen

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Reply with quote  #2 
Maybe the puffs of air with certain letters relate to the problems some sufferers have with them.
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Please resist the temptation to pick apart my post by quoting it piece by piece.
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Johnloudb

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Reply with quote  #3 
Very interesting stuff. Of course we use all kinds of sensory information to process sounds though. 
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gardennut

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Reply with quote  #4 

Hi Johnloud.......   Just a quick hello and to say I enjoyed your story in the Newsletter.  Are you still doing better?    Hope so,   Cheers,  Donna


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Donna Keddie
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Johnloudb

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Reply with quote  #5 

Hi Donna, thanks. I enjoyed writing it. I'm still making slow but consistent progress. Things have really improved for me the last few years.

Best,

John

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MirjamVonk

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Reply with quote  #6 

Thanks guys and hi Donna,

 

I found the following. Maybe an interesting read as well.

 

Love, Mirjam

 

 

Pebble splashes break the speed of sound

Jan 24 2010.

http://www.newscientist.com/article/mg20527444.700-pebble-splashes-break-the-speed-of-sound.html

 

IS IT a bird, is it a plane? No, it's a rock falling into a pool of water, but the jet of air it produces flies faster than a speeding bullet.

 

When an object such as a pebble drops into water, an air-filled cavity is created which ejects air at supersonic speeds, discovered Stephan Gekle at the University of Twente in the Netherlands, and colleagues.

 

Using high-speed photography, the team spotted a cavity of air forming in an hourglass shape - with the top of the hourglass at the surface of the water and its base at the sinking object. To measure the speed of air rushing out upwards, they marked the air with smoke before the splash.

Even though their camera took 15,000 frames per second, they still couldn't measure the fastest speeds directly, so they simulated the behaviour they had observed. They found that shortly before the cavity closes, the pressure of the air at the bottom of the hourglass becomes higher relative to the "neck". This difference pushes the air out at speeds faster than sound (Physical Review Letters, DOI: 10.1103/PhysRevLett.104.024501).

 

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Why Dropping a Stone Makes a Jet

Jan 23 2010.

http://focus.aps.org/story/v23/st3

 

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Just a stone's throw forms a supersonic jet

Objects hitting water can move air at the speed of sound

Jan 15 2010.

http://sciencenews.org/view/generic/id/54965/title/Just_a_stones_throw_forms_a_supersonic_jet

A stone hitting a pond can produce a tiny supersonic splash, a new study has found.

Researchers studying the shape of an air cavity made when an object hits a liquid noticed a similarity to the shape of the nozzles that are in supersonic jet engines. Sure enough, air escaping from the cavity can reach supersonic speeds, the team reports in a paper published online January 11 in Physical Review Letters

 

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Storm in een glas water

21 jan 2010.

http://www.kennislink.nl/publicaties/storm-in-een-glas-water

 

Voorwerp dat in water valt veroorzaakt supersone luchtstroom

Hoewel natuurkunde tegenwoordig vooral over hele kleine dingetjes en hele grote apparaten lijkt te gaan, biedt ook het alledaagse nog volop uitdagingen. Neem nou de simpele situatie waarin een steen in een plas stilstaand water valt. Met een supersnelle camera en een rookmachine brachten wetenschappers aan het licht dat zo’n plons gepaard gaat met het doorbreken van de geluidsbarrière.

 


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Mirjam Vonk
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MirjamVonk

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Reply with quote  #7 
Hi dear Milo,

Yes, I have received it just fine! Thank you so much for your nice card in return and for writing me.

Not many people take the time to send someone a handwritten card or letter anymore nowadays.  I think a handwritten card or letter is special, and so was yours, thank you Milo.

With love, Mirjam

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Mirjam Vonk
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