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Why Do Our Ears Pop When We Ride In Airplanes?

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You’re sitting on a plane destined for a far off place, sandwiched between two people, and you're doing your best to sit back and get comfortable. But as the plane takes off and makes its rapid ascent toward cruising altitude, a baby begins to cry, the people around you wince, and finally, it hits you—a buildup of pressure, tightening your ears and sinuses, that compresses your head like a vice that won’t let go. The plane continues upward until it stabilizes thousands of feet above the ground and then—POP!—your head feels fine.

Whether you’re in an airplane soaring through the sky, on an elevator heading to the top floors of New York’s tallest skyscraper, or making a deep dive underwater, your ears will most likely pop. The explanation for why this occurs is simple: It’s pressure. But what, exactly, is happening inside your ears?

Under Pressure

When a plane ascends, the air pressure in the cabin lowers at a rapid rate. This sudden change causes an irregularity with the pressure in the inner ear. At such high altitudes, the pressure pushes outward on the eardrum—the thin membrane between the external and middle ear that transmits sound—and causes the tension you feel in your head. (The pressure also reduces your ability to hear.)

One way to release this pressure is through the Eustachian tube, a 1.4-inch long cavity in the middle ear that connects the ears to the nose and throat. Yawning, swallowing, or even chewing gum opens the muscles of the Eustachian tube, causing air to fill the space and equalize that sometimes debilitating pressure caused by rapidly changing altitude. During that equalization, the air forcing into the tube makes that pesky popping or crackling sound, alleviating some of the discomfort the fluctuation caused.

Fancy Maneuver

When yawning or swallowing doesn’t do the trick, people use what is known as the “Valsalva Maneuver.” Named after Antonio Maria Valsalva, a 17th century Italian physician whose scientific specialty was the ear, the maneuver consists of closing the mouth, pinching the nose, and exhaling as if to blow up a balloon. It isn’t recommended, however, as it may cause barotrauma—damage to bodily tissue caused by a pressure difference inside and outside the body—or further auditory damage from the violent pressure equalization pushing outward.

After you’ve heard that pop, the pressure should be equalized, and the pain gone. You can watch some in-flight entertainment, or chow down on the packet of peanuts the flight attendants give you—at least until the descent, when, thanks to the rapidly increasing pressure in the cabin, you might have to go through the discomfort, and popping, all over again.

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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Name the Author Based on the Character
May 23, 2017
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