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Researchers discover way to allow 80 percent of sound to pass through walls

Researchers discover way to allow 80 percent of sound to pass through walls | Science ed | Scoop.it

A team of researchers in Korea has discovered a way to allow sound to pass through walls almost as if they were not there at all. As the group describes in their paper published in the journal Physical Review Letters, the technique involves drilling very small holes in a wall and then tightly covering them with a thin sheet of plastic.

In this new effort, the researchers sought to extend prior research done by Thomas Ebbesen and colleagues in 1998 where it was discovered that holes, made in a metal sheet that were smaller than the wavelength of light shone on it, allowed more light to pass through than expected—a property that has come to be known as extraordinary optical transmission. Subsequent research found the principle did not apply to sound waves due to rigid parts of the barrier reflecting back most of the applied sound. The researchers on this new team suspected that altering certain aspects of the barrier might allow for the property to hold for sound after all.

They began by drilling several holes (10 millimeters in diameter) in a 5-millimeter -thick piece of metal. Next, they placed a speaker on one side of the "wall" and a microphone on the other. With just the holes, they found the wall blocked sound almost as effectively as if there were no holes drilled in it. Next, they covered one side of the wall with a thin tensioned membrane (plastic wrap). After playing the sound again, the researchers discovered that the addition of the membrane allowed much more sound to pass through the wall—on average 80 percent more—almost as if the wall weren't there at all.

 

The membrane, the team explains, allows for "zero resistance" as the sound encounters the holes. At the resonance frequency of the membrane (1200 hertz), air moved in the holes as if it had no mass at all. That in turn allowed sound waves to move through very quickly. The sound in the holes was actually concentrated as it passed through, suggesting that the technique might be used as a way to magnify small signals. One application of this discovery could be walls that serve as security barriers.


Via Dr. Stefan Gruenwald
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Chris Upton + helpers's comment, June 24, 2013 1:57 PM
"80% more" than almost nothing, isn't much - perhaps it's mis-written
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TEDx Talk: This Camera Will Make You See With Your Ears. By Noam Galai (17:17)

TEDx Talk: This Camera Will Make You See With Your Ears. By Noam Galai (17:17) | Science ed | Scoop.it
Posted by Noam Galai on January 3, 2013 • 

Photo: Ingmar Bergman by Irving Penn • 

 

"Dr. Amir Amedi, brain researcher and Neurobiology professor from the Hebrew University in Jerusalem, developed a technology that lets blind people ‘see’ with their ears. In this TEDx talk (TEDxJerusalem) he shows how he managed to use a simple camera, and transform the video captured into sound waves that quickly become visual images in the brain."

...


FStoppers.com


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Spix's disk-winged bats use leaves as megaphones to boost the sound of their sonar calls

Spix's disk-winged bats use leaves as megaphones to boost the sound of their sonar calls | Science ed | Scoop.it

Bats are climbing inside curled leaves and using them to amplify sound, marking the first time an animal has been observed using a tool to increase its vocalization range. A recent study has shown that Spix's disk-winged bat uses the shape of the leaves to boost the sound of both incoming and outgoing calls.

 

The tiny bats — so named for cute little suction disks on their wings — roost inside curled-up leaves. To identify the correct roosting spot, they call out: when that call is met by a chirped response, they know they've found home. The study, published by the Proceedings of the Royal Society, found that both call and response sounds were amplified by the shape of the leaves. Outgoing replies from roosting bats were faintly boosted by the leaves' trumpetlike effect; incoming calls from flying bats were significantly increased in power as sound waves were funneled down the leaves' lengths.

 

The study also found that both of these calls were so significantly distorted by their leaf modulation that roosting bats wouldn't be able to understand who was making the sound. Christine Dell'Amore explains that roosting bats instead "respond indiscriminately" to calls of their species. Response calls, Dell'Amore says, are "more acoustically complex," meaning that despite leaf distortion, enough information gets through for a calling bat to successfully find his friends.


Via Dr. Stefan Gruenwald
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Detecting tunnels -- used to smuggle drugs, weapons, or people – is not easy

It seems reasonable to assume that it would be easy to use seismic waves to find tunnels dug by smugglers of drugs, weapons, or people, but this assumption is wrong; scientists are trying to get a better look at the ground around tunnels to learn why seismic data finds some tunnels but not others – and come up with a seismic detection process for the border and other areas where tunnels pose a security threat
It seems reasonable to assume that it would be easy to use seismic waves to find tunnels dug by smugglers of drugs, weapons, or people. This assumption is wrong.


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This is wild...check out this optical illusion, demonstrates how sound waves move

This is a great illustration of collective phenomena. If you look closely, each dot is just moving around in a regular circle; but because the different circles are out of phase with each other, when you back away you see waves steadily moving across the screen. It's a simple demonstration of how large-scale, collective phenomena can emerge from very simple small-scale behavior. Things like this happen all over the place: water waves and sound waves, for example, work in basically the same way, with the small back-and-forth motions of individual molecules leading to compression patterns moving through the air. 

Originally from http://i.imgur.com/ckxfccq.gif  , and found via +Jane Shevtsov and+W Younes.

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littlebytesnews's curator insight, June 28, 2013 2:27 AM

Pretty wild....

Conversations for Inquiring Minds's curator insight, June 28, 2013 10:04 AM

Once you see the waves you can't shut it down.  I didn't need to focs very hard either. 

 

Lately Nat Geo has had a show called Brain Games.  The information in the program teaches how the brain processes information and how some individuals can fool you due to their knowledge of how the Brain works.

 

Great show and fun article.

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Invisible force field gives touchscreens a whole new feel

Invisible force field gives touchscreens a whole new feel | Science ed | Scoop.it

Beams of ultrasonic sound waves project a force field in front of screens, making it feel as though a user is touching an invisible 3D surface.

 

Imagine waving your hand in front of a map on your computer screen and feeling a force push back against you. The strength of the force could be proportional to the population or crime rate, say, of each city you pass over.

 

Tom Carter and his colleagues at the University of Bristol, UK, will demonstrate just such a system this week at the User Interface Systems and Technology conference in St Andrews, UK.

 

Called UltraHaptics, it uses an array of 320 ultrasound speakers set behind a touchscreen to generate beams of high-frequency sound waves. The waves are linked to the software running the displayed content and interact to create hotspots that give different sensations as people move their hands.

 

"What you feel is a vibration. The ultrasound exerts a force on your skin, slightly displacing it. We then turn this on and off at a frequency suited to the receptors in your hand so that you feel the vibration," says Carter.

"A 4-hertz vibration feels like heavy raindrops on your hand," he says. "At around 125 Hz it feels like you are touching foam and at 250 Hz you get a strong buzz."

 

UltraHaptics could be used to make invisible sliders for in-car entertainment systems, Carter says, so drivers could feel their way to the desired volume. And people whose hands are often dirty, like chefs or mechanics, could use invisible haptics to flip through manuals or recipes.

"This ultrasound approach is great in that it tackles a hard problem in producing the sensation of a directed force in mid air," says Patrick Baudisch, who works on novel interactive technology at the University of Potsdam in Germany.

 

One problem remains, however: the sounds can be heard by dogs, which could cause all sorts of issues. Pooch owners should be able to rest easy though. "We can increase the frequency to take it out of that range," says Carter.


Via Dr. Stefan Gruenwald
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NASA releases images of Pakistan's quake-created 'Earthquake Island'

NASA releases images of Pakistan's quake-created 'Earthquake Island' | Science ed | Scoop.it
Amidst the destruction caused by the devastating earthquake in Pakistan that killed more than 500 people, a new island emerged from the depth of the sea. NASA has released images of the newly formed islet.

 

NASA has released before and after photos of a new terrestrial body that was born on September 24 during a quake that struck Pakistan. 

Called Zalzala Jazeera, or a an earthquake island, the terrestrial formation can now be found 380 kilometers from the earthquake’s epicenter in Paddi Zirr Bay near Swadar, Pakistan in the Arabian Sea.  

The first image of the island was taken  by NASA’s Earth Observing-1 satellite on September 26, while the second snapshot shows the same bay on April 17 with water and no landmass around the coordinates that the new island now inhabits.

 

According to scientists, the depth of the water level around Zalzala Jazeera stands at about 15 to 20 meters, stretching 75 to 90 meters across. It lies approximately one mile from the shore. Scientists say the island is nothing more than just a pile of mud, sand and solid rock that was caused by the forces of highly pressurized gas.

 

“The island is really just a big pile of mud from the seafloor that got pushed up. This area of the world seems to see so many of these features because the geology is correct for their formation. You need a shallow, buried layer of pressurized gas—methane, carbon dioxide, or something else—and fluids. When that layer becomes disturbed by seismic waves (like an earthquake), the gases and fluids become buoyant and rush to the surface, bringing the rock and mud with them,” Bill Barnhart, a geologist at the US Geological Survey told NASA’s Earth Observatory. 

 

The Earth Observatory says this is not the first island to have surfaced along the 700-kilometer-long coast over the past century.  Scientists predict that the new island will remain above surface for up to a year before sinking back into the Arabian sea.

 

The island rose out of the water during a 7.7-magnitude earthquake that struck Balochistan, just 69 km north-northeast of Awaran -  the nearest Pakistani city - on 24 September 2013. Over 300,000 people were affected by the quake, which caused over 500 deaths, and some 21,000 houses were destroyed.


Via Dr. Stefan Gruenwald
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