Engineers Design Device to Listen to Knees’ Snaps, Crackles, and Pops

We tend to associate creaking, popping joints with old age, but your joints make tiny little noises every time you move, no matter your age. These noises are so faint, we usually can’t hear them with the naked ear. But one team of engineers at the Georgia Institute of Technology (GIT) wants to listen in on the noises made by joints, and they built a device that lets them do just that. The team shared a report of their progress in the online journal IEEE Transactions on Biomedical Engineering.

The project started with a call for research proposals on rehabilitation technology from the Defense Advanced Research Projects Agency (DARPA). The military has a lot of motivation to advance rehab technology. From basic training to deployment, soldiers undergo intense physical stresses, whether that’s carrying hundred-pound backpacks, marching for miles and miles, or darting through an active war zone.

"What most people don't know is that musculoskeletal injuries of the knees and ankles are among the top reasons for discharge for active duty service members," GIT engineer and paper co-author Omer Inan said in a press statement.

But like products developed for NASA, technologies created with the military in mind often trickle down to civilians. Inan, for example, is not a career military man, but he was a discus thrower in college and has first-hand (or first-knee) knowledge of the strain athletes put on their joints. Although he retired from sports years ago, Inan can still feel—and hear—the damage in his knees.

He and his colleagues realized that those snapping, crackling, popping noises might be a good indicator of injury. They created a knee band outfitted with microphones and vibration sensors that record sounds in the air and inside the body.

Typical knee-popping sounds are one thing, but the in-body crunching and grinding noises are … well, kind of nauseating. Listen for yourself:

"It's a little bit like some kind of Halloween stuff happening,” Inan said. “You're listening to your bones rubbing on each other, or maybe cartilage."

The in-body noises of both healthy knees and damaged knees sound pretty disgusting, but they do produce different patterns of sound, which could make the knee band a great diagnostic device.

Though progress has been made, the device is not quite ready yet. Getting a clear recording can be hard; our joints are surrounded by fluid, which can dampen sound waves that emanate from the joint. Additionally, the recordings must be taken while a patient is moving, but that movement makes its own noises.

Inan and his colleagues will continue to test and improve their design, and the medical technology world will be listening closely.

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Feeling Anxious? Just a Few Minutes of Meditation Might Help

Some say mindfulness meditation can cure anything. It might make you more compassionate. It can fix your procrastination habit. It could ward off germs and improve health. And it may boost your mental health and reduce stress, anxiety, depression, and pain.

New research suggests that for people with anxiety, mindfulness meditation programs could be beneficial after just one session. According to Michigan Technological University physiologist John Durocher, who presented his work during the annual Experimental Biology meeting in San Diego, California on April 23, meditation may be able to reduce the toll anxiety takes on the heart in just one session.

As part of the study, Durocher and his colleagues asked 14 adults with mild to moderate anxiety to participate in an hour-long guided meditation session that encouraged them to focus on their breathing and awareness of their thoughts.

The week before the meditation session, the researchers had measured the participants' cardiovascular health (through data like heart rate and the blood pressure in the aorta). They evaluated those same markers immediately after the session ended, and again an hour later. They also asked the participants how anxious they felt afterward.

Other studies have looked at the benefits of mindfulness after extended periods, but this one suggests that the effects are immediate. The participants showed significant reduction in anxiety after the single session, an effect that lasted up to a week afterward. The session also reduced stress on their arteries. Mindfulness meditation "could help to reduce stress on organs like the brain and kidneys and help prevent conditions such as high blood pressure," Durocher said in a press statement, helping protect the heart against the negative effects of chronic anxiety.

But other researchers have had a more cautious outlook on mindfulness research in general, and especially on studies as small as this one. In a 2017 article in the journal Perspectives on Psychological Science, a group of 15 different experts warned that mindfulness studies aren't always trustworthy. "Misinformation and poor methodology associated with past studies of mindfulness may lead public consumers to be harmed, misled, and disappointed," they wrote.

But one of the reasons that mindfulness can be so easy to hype is that it is such a low-investment, low-risk treatment. Much like dentists still recommend flossing even though there are few studies demonstrating its effectiveness against gum disease, it’s easy to tell people to meditate. It might work, but if it doesn't, it probably won't hurt you. (It should be said that in rare cases, some people do report having very negative experiences with meditation.) Even if studies have yet to show that it can definitively cure whatever ails you, sitting down and clearing your head for a few minutes probably won't hurt.

Ted Cranford
Scientists Use a CT Scanner to Give Whales a Hearing Test
Ted Cranford
Ted Cranford

It's hard to study how whales hear. You can't just give the largest animals in the world a standard hearing test. But it's important to know, because noise pollution is a huge problem underwater. Loud sounds generated by human activity like shipping and drilling now permeate the ocean, subjecting animals like whales and dolphins to an unnatural din that interferes with their ability to sense and communicate.

New research presented at the 2018 Experimental Biology meeting in San Diego, California suggests that the answer lies in a CT scanner designed to image rockets. Scientists in San Diego recently used a CT scanner to scan an entire minke whale, allowing them to model how it and other whales hear.

Many whales rely on their hearing more than any other sense. Whales use sonar to detect the environment around them. Sound travels fast underwater and can carry across long distances, and it allows whales to sense both predators and potential prey over the vast territories these animals inhabit. It’s key to communicating with other whales, too.

A CT scan of two halves of a dead whale
Ted Cranford, San Diego State University

Human technology, meanwhile, has made the ocean a noisy place. The propellers and engines of commercial ships create chronic, low-frequency noise that’s within the hearing range of many marine species, including baleen whales like the minke. The oil and gas industry is a major contributor, not only because of offshore drilling, but due to seismic testing for potential drilling sites, which involves blasting air at the ocean floor and measuring the (loud) sound that comes back. Military sonar operations can also have a profound impact; so much so that several years ago, environmental groups filed lawsuits against the U.S. Navy over its sonar testing off the coasts of California and Hawaii. (The environmentalists won, but the new rules may not be much better.)

Using the CT scans and computer modeling, San Diego State University biologist Ted Cranford predicted the ranges of audible sounds for the fin whale and the minke. To do so, he and his team scanned the body of an 11-foot-long minke whale calf (euthanized after being stranded on a Maryland beach in 2012 and preserved) with a CT scanner built to detect flaws in solid-fuel rocket engines. Cranford and his colleague Peter Krysl had previously used the same technique to scan the heads of a Cuvier’s beaked whale and a sperm whale to generate computer simulations of their auditory systems [PDF].

To save time scanning the minke calf, Cranford and the team ended up cutting the whale in half and scanning both parts. Then they digitally reconstructed it for the purposes of the model.

The scans, which assessed tissue density and elasticity, helped them visualize how sound waves vibrate through the skull and soft tissue of a whale’s head. According to models created with that data, minke whales’ hearing is sensitive to a larger range of sound frequencies than previously thought. The whales are sensitive to higher frequencies beyond those of each other’s vocalizations, leading the researchers to believe that they may be trying to hear the higher-frequency sounds of orcas, one of their main predators. (Toothed whales and dolphins communicate at higher frequencies than baleen whales do.)

Knowing the exact frequencies whales can hear is an important part of figuring out just how much human-created noise pollution affects them. By some estimates, according to Cranford, the low-frequency noise underwater created by human activity has doubled every 10 years for the past half-century. "Understanding how various marine vertebrates receive and process low-frequency sound is crucial for assessing the potential impacts" of that noise, he said in a press statement.


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