humans can only hear a finite range of the sound spectrum. sounds that are above the frequency of human hearing are referred to as “ultrasound.” whereas sounds that are below human hearing are called “infrasound.”

the ncpa, located on the university of mississippi’s campus in oxford, has developed a method to detect tornados using infrasound, sounds below the frequency of human hearing.  

there has never been a perfect method for detecting tornadoes. in fact, only one method works on a consistent basis.

“the easiest way to detect a tornado, in this day in age, is through people’s eyes and calling in their locations,” said dr. roger waxler, senior scientist and group leader for the infrasound research.  

waxler holds a phd in physics from columbia university, and has a professional background at numerous renowned institutions in the field.

the infrasound group at the ncpa are getting a better grasp on when tornados form, where they land, and where they move to, to provide more accurate information for the public before a tornado hits and to provide more images of these, he said. in addition to affecting the area of the midwest traditionally known as “tornado alley,” the southern united states, including mississippi, also is often hit hard by tornadoes.  

according to noaa and the national weather service’s storm prediction center, mississippi averages 45.1 tornado touchdowns a year. this number comes from certain features that the tornado produces, and forecasters are trained to look for these distinguished features.

the state ranks in the top 10 nationally for number of tornado touchdowns each year, with a variety of serious and non-serious effects. they usually hit the worst between the months of january and may, and can occur all the way through november.

ncpa scientists have been researching the use of sensor arrays, which they developed on campus, to pick up sound and pinpoint the tornadoes and track them through infrasound.  with their new technology, they have also been able to pick up information, through doppler radars, identifying wind speed and rotation of the tornado, within thunderstorms.  

“we get to go trounce around in national forests, putting out sensors, and we have a lot of fun,” dr. craig hickey, interim director of the ncpa, said with a laugh. the sensors he is referring to are placed in an array.  by measuring the time at which a signal arrives at each array placement, scientists can determine the direction of the signal.

dr. hickey, dr. waxler, and the rest of the researchers at the ncpa are optimistic about the direction of the tornado research.  

“there’s still a lot of questions [to be answered], and progress to be made, but the information we do have is certainly promising,” said waxler.

interviews:

dr. craig j. hickey (geophysics)

interim director of the national center for physical acoustics

senior research scientist ii

research associate professor of geological engineering and physics

662-915-5963

chickey@olemiss.edu

dr. roger waxler

senior research scientist ii

research associate professor of physics & astronomy

662-915-5963

rwax@olemiss.edu

instead of testing nuclear explosions, chemical explosions are being used in replacement to avoid exposing a severe amount of radiation.

dr. roger waxler, a research associate professor of physical acoustics and astronomy, said, “chemical sound wave research started in the 1950’s with allan pierce, a graduate of mit in the physics department. pierce got a job at rand corporation, were they produced signals that would go around the world a couple of times, but failed to understand what the signals meant at large distances.”

currently, large blast signals are different compared to the blasts in the 1950’s, so the university of mississippi’s national center of physical acoustics created technology to gain more intelligence on chemical sound waves.

the national center of physical acoustics had been using sensors to detect sound waves and signals until there was a new way. “hank bass a former colleague at the center, created a laboratory quality, high-end, infrasound microphone to have a better understanding on chemical sound waves, before passing away,” waxler said.

the universities center has been working to further enhance their research with the technologies in use and any new upcoming technologies.

waxler said, “the university of mississippi’s center has installed stations in america within, alaska, central washington and southern california. they have also orphaned stations outside the country working with the british. stations can be found in antarctica, palau and diego garcia, as well.”

ncpa is working with the countries all over the world to retain more information on seismic signals, making them global.

he also explains, “the maintenance and operation of these stations have been given over to university of alaska, but ncpa has continued to maintain the research.”

the focused research extends off the work allan pierce did, condensed to the smaller explosion, in effect today. “it involves mathematical modeling as well as finding large explosions to test models. in addition, the sensors needed to be converted to infrasound microphones that are able to respond to sub audible frequency and can sit out in the field under horrible conditions, and the sensors we developed satisfy that,” waxler said. 

in the sense of if a nuclear bomb were to blow up, waxler said, “it is widely noted that we are going to know about it, and the world, as a whole, is going to do something about it.”

not only do scientists and researchers have access to information about the location of the explosion, but they are able to receive a great amount of information on the sound waves and the impact the explosion would have.