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Mimicking the Super Hearing of a Cricket-Hunting Fly

Ormia ochracea is a little, yellow fly of the American south whose breeding strategy has an outsize ick factor. It deposits its larvae on the bodies of male crickets. The larvae then eat their way into their unwilling hosts, and devour them from the inside.

What is most remarkable, though, is that the female fly locates the crickets by sound, homing in on the he-cricket’s stridulations (the chirping that results from the wings rubbing together) with uncanny accuracy. The cricket’s chirp is a smear of sound across the scale from the 5 kilohertz carrier frequency to around 20 kHz. And, as anybody who has tried to evict a passionate cricket from a tent or cabin knows, the sound is maddeningly hard to pinpoint.

With an auditory apparatus—let’s call them ears—only 1.5 millimeter across, ochracea pulls off a major feat of acoustic location; a number of engineering groups are working on devices to duplicate the fly’s sensitivity.

Now, a team at the University of Texas at Austin has built a prototype replica of O. ochracea’s ear. Michael L. Kuntzman and Neal A. Hall, researchers in the school’s electrical and computer engineering department, describe the device and its performance in Applied Physics Letters.

The fly’s ears are very different from those of humans. Human ears are typically separated by about 21 to 22 centimeters—about 625 microseconds apart at the speed of sound (though of course it varies with temperature and humidity). We judge sound direction by assessing ear-to-ear differences in phase and volume. We can distinguish time differences of as little as 10 microseconds, and the phase-difference calculation is useful mainly for lower-frequency sounds—those with wavelengths longer than 21 cm. In this range, we can locate a sound source to within about 1 degree if it is dead ahead, or 15 degrees if it is off to the side.  As frequencies rise above about 1600 Hz (a very sharp G above high C), the wavelength is shorter than the ear-to-ear separation, and we fall back on using the volume difference alone to approximate the source’s position.

The fly’s ear, on the other hand, is 4.3 microseconds wide at the speed of sound, and it can distinguish phase delays much smaller than that in sounds coming in from nearly ahead or behind.

The secret is the physiology of the ochracean ear, whose centerpiece is an elastic plate that pivots on a central support. This structure responds to incoming sound waves by resonating in two distinct modes. You can picture them, albeit on an obviously much larger scale, by standing with your arms outstretched to either side. First, raise one arm while lowering the other, like the ends of a see-saw; that’s the first mode. Now move your hands up and down together, flapping like a bird; that’s the second mode.

In the fly’s ear—and in the Kuntzman-Hall device—each mode responds to a different parameter of the incoming wave. The see-saw action responds only to the x-component of the incoming pressure gradient, indicating, say, a how a high-pressure compression crest at the tips of your fingers shades into a low-pressure trough at your elbow. It tracks the changes only along the one dimension of your arm, though, and reveals nothing about the omnidirectional strength and structure of the wave. The flapping mode, on the other hand, responds only to omnidirectional pressure—the sound volume, for example, or the overall pressure on your body—and reveals nothing about the wave's direction. In the fly's ear, both modes superpose to create a composite displacement of the membrane, so the trick is to break this signal down into its see-saw and flapping components..

The fly can individually quantify the displacements of the right and left sides of its pivoting-beam auditory membrane. Then the fly's neural network subtracts the displacement of the left-side channel from the displacement of the right channel to extract the first-mode see-saw signal; this shows the incident angle of the incoming sound. At the same time, the fly's brain adds the left- and right-channel signals to yield the second-mode flapping displacement. This reveals the omnidirectional sound pressure (a clue to distance).

The UT researchers etched a spring-loaded, 1.5-mm-by-2.5-mm pivoting beam into silicon, with a lead-zirconate-titanate piezoelectric film painted on the supporting springs to sense displacement. In experiments, Kuntzman and Hall have read and analyzed the output just as the fly’s brain does. The prototype can resolve the direction of high-frequency sound sources to within 0.35 degrees for sounds in its directional “sweet spots,” and to within about 6 degrees in its less sensitive zones. (The imprecision, their paper says, is mainly due to some imperfections or asymmetries in the prototype.)

“Synthesizing the special mechanism with piezoelectric readout is a big step forward towards commercialization of the technology," said Hall, an assistant professor. There are sure to be defense applications—after all, the research is funded by the U.S. Department of Defense's Advanced Research Projects Agency (DARPA)—as well as potential for commercial products like hearing aids. 

WikiMusical Travels the Web through Song

Twenty years ago only a quarter of U.S. homes had a PC and the biggest media decision facing a child was Sega Genesis or Super Nintendo. Now, media and the Internet are experienced in a million different ways by a million different people—but can you sum up its essence? Blake Harris thinks he can: with musical theatre.

Harris, author of the video game history Console Wars, grapples with defining the Internet experience and its ever-changing landscapes in a new show called WikiMusical, playing until Saturday as part of the 2014 New York Musical Theatre Festival. Harris wrote the lyrics and book for the musical, which is a meandering journey through the sites, memes, and trends that make up the Web. It’s silly and surreal, and hidden inside is an exploration of the ways we’re making the Internet our home.

“For musical theatre, there’s something that’s almost communal about the experience,” says Harris, “and the story of the tech age is such an interconnected story. It touches upon a lot of different threads—one of the great things about the Internet is that there’s a seemingly infinite number of rabbit holes you can go down. The story is an attempt to make a narrative out of all of it.”

The show starts in a simpler time, with siblings based on Harris and his brother getting a Gateway computer from an eccentric Santa Claus. It quickly jumps to the present: the grown brothers are pulled bodily into the modern Internet where they must defeat the sinister and seductive Spam King to save the Web and return home, mending their relationship along the way. On their journey they meet a blogger on a quest and a cast of unlikely online characters—including the cats that (evidently) invented the Internet,  Mario and Luigi, and Morgan Freeman.

The show has strong acting and the songs are often catchy, although the narrative thread can sometimes get lost among the different encounters and gags. In fact, narrative is one of the challenges this show takes on: how to pull the universal tropes of a hero’s journey from the nebulous, multi-faceted, constantly evolving Internet.

According to Harris: “We live in such a niche age, whether it is websites or television channels, that having flagship websites or central hubs is more important than ever to have those shared communal experiences.” Using these well-known sites along with familiar memes and web personalities as landmarks, Harris takes the audience on a State of the Internet tour: an attempt to capture the zeitgeist of what we all experience when we experience the Internet, and the communities we’ve created.

The show is at its strongest when it explores the Internet’s collaborative nature and makes us stop and think about what we’re building. Harris sees Wikipedia as a window into that world under construction, which is why he kept the title even as the plot ballooned beyond just the editable encyclopedia.

“Wikipedia is basically this giant Ouija board that we all put our hands on and try to create an information network together,” he says. “It represents the best and worst of the technological age.”

Camera-Filled Dome Recreates Full 3-D Motion Scenes

Those thrilling moments when a soccer player kicks home the winning goal in the World Cup final or Beyonce debuts new dance choreography in concert might someday be recreated in full 3-D motion down to the smallest piece of confetti and played back from almost any angle. Such a possibility comes from a new motion-capture technique capable of reconstructing scenes captured by more than 500 video cameras mounted inside a two-story geodesic dome.

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Bitcoin Gets Its Own TV Network

This September, if all goes according to plan, the Bitcoin blockchain will take to the radio waves in Finland. The project is called Kryptoradio. It's the result of a partnership between Koodilehto, a Finnish co-op specializing in open technology development, and another group that was responsible for developing and encouraging the adoption of the alternative digital currency known as FIMKrypto.

Together they have secured the rights to transmit updates to the Bitcoin blockchain across digital terrestrial television in Finland. To do so, they will use Digita, a Finnish network that provides coverage for approximately five million people—95 percent of the population, according to their estimates. The transmissions are scheduled to continue for two months as part of a pilot program, and longer if they can find the funding for it.

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Freeman Dyson Predicts the Future

Interactive Video: Choose the sections you want to watch by clicking on subjects on the video’s menu screen.

When we started making a list of visionaries to interview for our special issue commemorating IEEE Spectrum’s 50th anniversary, Freeman Dyson was one of the first names to come up.

The celebrated physicist’s career got off to a quick start in the late 1940s, with a critical contribution to the then-nascent field of quantum electrodynamics. Since then it’s ranged far and wide, touching on subjects as varied as solid-state physics, biology, and climate change.

But for many, Dyson is known for his most speculative ideas. He is the man for whom the Dyson sphere is named—a hypothetical structure, built by an alien civilization, that could capture most or all the energy emitted by a star (and leave a telltale excess of infrared light that could be picked up by our telescopes). Dyson was also one of the key players on Project Orion, which ran from 1958 to 1963 and which conceived of a spacecraft, powered by a series of controlled nuclear explosions, that could have potentially carried humans to Saturn by 1970.

We wanted to see what this bold and imaginative thinker might have to say about humanity’s next 50 years. He welcomed IEEE Spectrum to his office at the Institute for Advanced Study in Princeton, N.J., last October, just a few days after a celebration honoring his 90th birthday.  

In the video posted here, you’ll find an interactive version of his discussion with Associate Editor Rachel Courtland. Topics include the possibility of finding extraterrestrial life, the future of space exploration, and what might become of our efforts to better understand the human brain. One of Dyson’s wilder ideas is a sort of “super-chicken,” a biological system that could allow people without a wealth of natural resources to grow their own chairs, tables, and other objects.

Toward the end of the discussion, Courtland couldn’t help but ask Dyson what it’s like to make predictions about the far future. “The point about prediction is not that it’s true. Prediction is just either a warning or a hope,” he responded. “Predictions should never claim to be true. But you can certainly claim that they’re possibilities you ought to think about.”

Leaked British Spy Catalog Reveals Tools to Manipulate Online Information

No online communication is for your eyes only in the age of Internet surveillance by government spy agencies. But a leaked British spy catalog has revealed a wide array of online tools designed to also control online communication by doing everything from hacking online polls to artificially boosting online traffic to a particular website.

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UK: Let's Make a Spaceport!

In a bid for rapid-fire relevance in the emerging private spaceplane industry, the UK government announced its intent to open a commercial passenger spaceport within four years. Eight airfields have been singled out as the British Isles’ answer to New Mexico's “Spaceport America” — one each in England and Wales, with the remaining six in Scotland. 

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An A for Raspberry Pi B+

This week the world’s most popular—and one of the world’s least expensive—home hobbyist computer kits just got upgraded.

The Raspberry Pi B+ retains its down-to-earth US $35 price. And it adds to its impressive arsenal of smartphone level computing power an additional two USB2 ports, a MicroSD storage slot (in place of the older SD card slot) plus lower power consumption and eight more hack-friendly general-purpose input-output pins.

Originally launched in 2012 as a low-priced, credit-card sized microcomputer aimed at the education and hobbyist markets, the Raspberry Pi has sold more than 3 million units to date, according to the nonprofit Raspberry Pi Foundation in Cambridge, U.K. (Cambridgeshire is also home to the computing world’s other great revolution in a tiny package, the ARM core processors that now — to Intel and AMD’s chagrin — comprise the CPU centerpiece of nearly every smartphone and tablet around the world today.)

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Quantum Computing IPO on the Horizon

Investors longing to own a piece of the quantum computing future could get their chance in the next several years. A stock market listing could be on the way for D-Wave Systems, the Canadian company that has built what it describes as the world's first commercial quantum computers.

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