When rescuers scramble to find survivors in a collapsed building, the routine is methodical: Clear debris, stop to listen for signs of life, go back to work.
Three researchers at Penn State University think that they have a better way to speed up the rescue effort.
By implanting a microphone and transmitter inside a baseball, members of the university’s acoustics program say they can listen for survivors in the pile while work is going on above.
“It’s something that could be done very quickly at low risk to the rescuer -- he doesn’t have to go into a dangerous area and lay cables,” said Thomas Gabrielson, senior research associate at Penn State’s Applied Research Laboratory and associate professor of acoustics. “If it doesn’t come back, it’s not a problem. These are cheap enough that if the pile breaks down, fine, you just leave it there.”
Gabrielson, acoustics department Chairman Anthony Atchley and doctoral student Matt Poese came up with the idea in September 2001, when they helped search for World Trade Center survivors.
The survivors had been extracted by the time the Penn State team began its work Sept. 18. By recording sounds at the northwest corner of the pile, they found that despite construction noise on the surface, just a few feet below, conditions were quiet enough that a microphone could pick up signs of life. Their findings were published in the January issue of the Journal of the Acoustical Society of America.
But the researchers realized the limitations of current sound-sensing technologies. Most rescuers teams simply have a microphone at the end of a long cable. It’s heavy and expensive, and extending the cable into the rubble can put rescuers in danger. Even then, it’s virtually impossible to get the microphone below the surface and away from the noise that would drown out sounds of survivors.
“Before we went to the World Trade Center, we felt that there would be these big, huge, open voids in the wreckage, where you could conceivably lower a microphone on the end of a cable,” Poese said. “That just doesn’t exist. It’s a twisty-turvy, tortuous pile of rubble.”
So cables were out. But if a wireless microphone could be put into the pile, rescuers could listen continuously to any signals coming from inside.
“A ball could find its way down very deeply -- just bounce, bounce, bounce, bounce, bounce,” Poese said.
Their first prototype, Gabrielson said, was inserted in a spongy, foam ball. But that was too light -- they couldn’t throw it far enough or accurately enough. A baseball from a sporting goods store proved the perfect solution -- light, durable, easy to throw.
Each rescuer might carry half a dozen such devices. At a site, rescuers would simply take out a ball, flip a switch and throw the ball into the rubble. A worker with a scanner could monitor all the radio transmitters at once and, by keeping track of which ball was thrown where, rescuers would have an idea where to look if they detected a signal.
“It would be a tremendous tool to save lives,” said Antoine Ataya, professor of engineering at Roger Williams University and a 17-year veteran of U.S. Navy search-and-rescue teams.
Ataya said the twisted metal found in building rubble might interfere with radio signals from the transmitter.
But Gabrielson said the group was working with different antennas that might mitigate that problem. They’re also experimenting with infrared sensors and a two-way radio system that would allow rescuers to talk with trapped survivors, he said.