Tag Archives: infrasound

Scientists analyze tornadoes in infrasound

Tornadoes can produce infrasounds, and those infrasounds can be used by scientists to “peak in” on the violent phenomena.

Composite of eight images shot in sequence as a tornado forming in Kansas in 2016. Image credits: Jason Weingart / Wikipedia.

A few decades ago, researchers realized that along with the very big ‘boom’, nuclear explosions also produce sounds — some of them at infrasound frequencies. Because infrasounds decay so slowly, they can travel around the Earth several times and can, therefore, be used to track nuclear tests.

Now, researchers are using the same approach to track down tornadoes, using infrasounds. During the 175th Meeting of the Acoustical Society of America, Brian Elbing, assistant professor of mechanical and aerospace engineering at Oklahoma State University, says that we can predict when and how a tornado will form, using infrasound detectors.

Tornado-producing storms can emit infrasound more than an hour before “tornadogenesis,” or tornado formation. Picking up on these waves could improve the accuracy of tornado alerts.

“By monitoring tornadoes from hundreds of miles away, we’ll be able to decrease false alarm rates and possibly even increase warning times,” Elbing said. “It also means storm chasers won’t need to get so close.”

[panel style=”panel-default” title=”Tornado formation” footer=””]No two tornadoes are the same, but all tornadoes require on specific conditions to form.

It starts when sunshine heats the ground, which causes pockets of air to rise. If the atmosphere is unstable, the pockets can rise to great heights, resulting in the development of much deep, strong currents of ascending air (updraughts) and storm clouds.

If the atmospheric winds are strong enough, the stormy updraughts can start to rotate, and tilt to become vertical.

Eventually, the rotation may become so strong that a narrow column of violently rotating air forms — thus, a tornado is born.[/panel]

An illustration of generation of infrasound in tornadoes by the Earth System Research Laboratory’s Infrasound Program.

In order to do this, Elbing and his team deployed three infrasound microphones arranged in a triangle, each spaced about 200 feet apart. The key features of these microphones are their ability to zoom in on very specific frequencies and to filter out any unwanted noise.

“First, these are larger for greater sensitivity to lower frequencies,” Elbing said. “Second, we need to get rid of wind noise. … We seal the microphone inside a container with four openings. A soaker hose — just like the ones used in gardens — is attached to each of these openings and stretched out in opposite directions.”

Of course, this would work best in areas which are prone to tornado formation, improving the alarm systems. A significant problem in such tornado-prone areas is that most tornado alarms are false — and as a result, are often ignored. With the infrasound technology, authorities could issue accurate alarm warnings and save lives. To make things even better, it can be used in tandem with existing technologies.

“Since infrasound is an independent data source, combining it with existing methods should help reduce false alarms,” said Elbing. “Today, 75% of tornado warnings are false alarms and tend to be ignored.”

Researchers already have their eyes on a particular test zone: Dixie Alley — the areas of the southern United States that are particularly vulnerable to strong or violent tornadoes. From there on, the technology could be deployed in much greater areas such as the infamous Tornado Alley.

“This is especially true for Dixie Alley, which isn’t known for the largest tornadoes but frequently has the most fatalities,” Elbing said. “Complex terrain, irregular road patterns, and nighttime tornadoes prevent storm chasers from observing these tornadoes, so long-range, passive monitoring for tornadoes will provide invaluable information about their formation processes and life cycle.”

Results have not yet been peer-reviewed.

Wind Turbines are quieter than a heartbeat, study finds

Among the criticism that wind energy gets, one main idea some people complain about is that wind turbines are noisy; some people have even went as far as to claim that even though most of the created noise is way below the range of human hearing (infrasounds), it can cause health problems, including heart issues and vertigo. Now, a study conducted by acoustical experts from Australia has shown that this idea is nothing more than pseudo science mumbo jumbo.

Picture Source.

Picture Source.

The Association of Australian Acoustical consultants found that that infrasound generated by wind turbines is less loud than the infrasound created by a human heartbeat. Even though the noise increases as the wind speed increases, you’re never going to hear it – it will always be masked by the natural noise of the wind as it passes through the environment. The acoustic engineers showed that “those investigations conclude that infrasound levels adjacent to wind farms are below the threshold of perception and below currently accepted limits set for infrasound.”

So even though the created noise is relative, people are subjected to far more significant sources of noise every day in every urban environment – the sound of cars, aircraft, wind, and waves – all do much more noise than wind turbines, and all are still in the tolerated limits.

“Our environment has lots of infrasound already in it, the levels generated by wind farms from our point of view are quite low in comparison and they’re no higher than what is already out there in the natural environment. … People themselves generate infrasound through things like their own heartbeat, through breathing and these levels of infrasound can be substantially higher than an external noise source.”

So why did people believe that it was the turbines causing them harm? Some even went to the doctors reporting symptomes of what came to be called “Wind Turbine Syndrome”. As it turns out, they were simply suffering from a nocebo (the negative, opposite of a placebo); people simply think they hear sounds which will make them sick, and they suggestion themselves into becoming sick. The human mind is a wonderful place.

Picture Source

Picture Source

Pigeon Bermuda triangle explained

Birds may not be the smartest bunch out there, but man do they know how to navigate! Pigeons can get around towns and even  continents with stunning accuracy – except for a particular spot in New York.

flying pigeon drawingWhenever homing pigeons were launched from that particular spot, they would always get lost. They could easily go from Europe to Asia and Africa, but that particular area was like a Bermuda Triangle to them. But now, new research suggests that birds are using low frequency sounds to find their way around – and they cannot hear the rumble at this US location.

In order to navigate, they use infrasound—low-level background noise in our atmosphere—to fly by “images” they hear, practically creating acoustic maps of the environment. Scientists have long suspected that birds use this method to for navigation, but until U.S. Geological Survey geophysicist Jonathan Hagstrum in Menlo Park, California, became intrigued by the unexplained loss of almost 60,000 pigeons during a race from France to England in 1997, no one actually pinpointed the phenomena. The race went bust just as the birds were crossing the route of a Concorde, and Hagstrum wanted to know why.

“When I realized the birds in that race were on the same flight path as the Concorde, I knew it had to be infrasound,” he says.

Concorde airplanes are now retired, but they were the fastest commercial airplanes to ever fly, traveling with speeds faster than the speed of sound, generating a sonic boom in the process – a sonic boom which interfered with the birds’ navigation.

In a paper published today in The Journal of Experimental Biology, Hagstrum correlates the trajectory of sound waves at release sites with the pigeons’ flight performance. He also showed that at that particular site in New York, the space geometry and background rumble covers the sounds used by birds.

“Jersey Hill was a bad spot for Cornell birds,” Hagstrum says. “The geometry of the area conspired to create a sound shadow.” On the single day in August 1969 that the birds returned home, there was a temperature inversion that bounced sound back to the release site, allowing the pigeons to navigate.

What’s surprising is that this study came from a geophysicist – not the typical area of activity for him; however, other researchers were thrilled by the results.

“I think it’s very convincing evidence that infrasound is a component of information birds use,” says Alfred Bedard, a physicist at the Cooperative Institute for Research in Environmental Sciences in Boulder, Colorado, who wasn’t involved in the study. “The open area is what infrasound they find most useful.” Still, “these results aren’t surprising,” he says. “If creatures have information in their environment that’s important to their survival, they would sense it.”

Via ScienceMag