Nov 3, 2016 | By Benedict

Researchers have developed 3D printed Lego-like bricks that can create acoustic holograms—3D shapes made of sound—for applications like entertainment, medicine, and wireless charging. The bricks are made using a conventional 3D printer and function as the pixels of the hologram.

Testing the 3D printed bricks in front of a sound-absorbing wall

Anyone familiar with the Star Wars franchise will have a rough idea of what a hologram looks like: a projected figure appears in mid-air, with specific lighting conditions rendering the image three-dimensional and lifelike. But while optical holograms are now part of pop culture—if not your average Skype call—acoustic holograms are the subject of a relatively new field of scientific study. The concept of an acoustic hologram is similar to that of an optical hologram, but with sound waves, not light, being dispersed into complex 3D shapes. Creating such holograms has proven to be a costly and demanding exercise, however, thanks to new scientific research documented in the journal Scientific Reports, that could be about to change.

A team of researchers led by Steve Cummer, a professor of electrical and computer engineering at Duke University in North Carolina, has developed a new method for creating accurate acoustic holograms. The secret? 3D printed Lego bricks. Previous approaches to creating acoustic holograms have involved complicated arrays of speakers and electronics, but Cummer’s research team has discovered that walls of 3D printed bricks can provide a simpler yet equally effective means of bending sound waves into complex shapes. “What we've shown is that you can use carefully designed and engineered structures to create a very complicated sound field from a very simple source,” Cummer explained.

Using the 3D printed bricks to create an "A"-shaped acoustic hologram

Where older methods of producing acoustic holograms involved precisely tinkering with the speakers and electronics used to manipulate the source sound itself, the new 3D printed brick technique changes the sound when it’s already on its way—by placing the brick structure in front of the source to manipulate the transmitted sound into new shapes. “This is a lot like a holographic sheet that you put in front of a light, and what gets transmitted is a much more complicated sound field,” said Cummer. “So, it doesn't require any extra sources—it's just an add-on to whatever sources you already have, and it's relatively easy to make.”

To create the 3D printed bricks, the researchers used various metamaterials with precisely engineered microstructures. Using a conventional 3D printer, the researchers made 12 different bricks out of these metamaterials, with the bricks each able to slow down sound waves at a different rate. The 3D printed bricks, which function as the “pixels” of the hologram, offer a more power-friendly, simple, and stable means of creating acoustic holograms, and could be used in a number of fields. To demonstrate the efficiency of the method, the researchers were able to create a 256-pixel hologram that turned a uniform sound wave into a sound field shaped like the letter “A,” as well as a lens-like second hologram that focused sound energy onto multiple circular spots of different sizes.

The 3D printed bricks could be used to improve audio entertainment systems

3D sound shapes are not visible to the human eye, but creating such shapes can be useful in a number of fields, including entertainment, where consumers can benefit from precisely controlled sound shapes. “Speakers don't just convey information on frequency and pitch; they also give you spatial information,” explained Yangbo “Abel” Xie, a doctoral student in Cummer's laboratory and first author on the research paper. “If you have your iPhone playing back a cello suite, it sounds like a single speaker playing back a cello suite. One potential application is that we can use this hologram to reconstruct a better acoustic scene, where your sense of spatial information of sound is more real.”

In addition to their entertainment potential, the 3D printed brick holograms could also be used to manipulate ultrasonic waves. Ultrasound is often used for medical imaging, and the compact, energy-efficient brick system could provide medical device companies with useful alternatives to current equipment. To repurpose their method for ultrasound, the researchers had to shrink their 3D printed bricks to roughly 1/100 their normal size, since ultrasonic waves operate at much shorter wavelengths. To do so, they collaborated with scientists at MIT, together printing a number of millimeter-sized bricks with tiny internal features. According to Xie, the bricks could also be used to wirelessly charge phones.

Medical ultrasound devices could benefit from the new research

These 3D printed “Lego bricks” might not be so fun for kids, but with better home entertainment systems and medical devices on the horizon, they might provide a great deal of fun for scientists.

 

 

Posted in 3D Printing Technology

 

 

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Shandor wrote at 11/11/2016 3:34:08 PM:

Sounds like they're about to reinvent the mechanism inside the sperm whale's bulbous head, which one researcher says is used to project a beam of sound powerful enough to stun its prey, the giant squid, at a distance.



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