ABLE earplugs could protect against bomb blasts

APL engineers invented the inexpensive plugs

  • Dan Simon holds a pair of the ABLE (Anti-Blast Ear) plugs. A cross-section of one plug shows a pop-it ball that blocks a shock wave.
Dan Simon holds a pair of the ABLE (Anti-Blast Ear) plugs. A cross-section… (Barbara Haddock Taylor,…)
September 15, 2013|By Tricia Bishop, The Baltimore Sun

Sometimes it's the simplest ideas that have the biggest impact, and Dan Simon is hoping his will prevent the hearing damage suffered by thousands of military personnel — the top reported service disability in the war on terror.

Simon, an engineer at the Johns Hopkins Applied Physics Lab in Laurel, and several of his colleagues have modified a generic set of rubbery, orange earplugs to develop an inexpensive "Anti-Blast Earplug."

Simon says the device, which the team has tentatively named the ABLE, allows wearers to hear normally until there's an explosion, such as those created by an improvised explosive device, or IED, the signature weapon of the enemy in Afghanistan and Iraq.

Then the plugs spring into action.

Each is shaped like a hollow Goldfish cracker, with openings at each end that allow most sound to travel through. But a tiny and very lightweight little ball — called a poppet — inside the plug stops up the hole closer to the wearer's eardrum as soon as blast waves hit it, acting as a protective check valve.

"It is that straightforward, at least in principle," said Simon, an affable father of four.

Other sound-modulating, high-tech plugs do the same thing, but they can cost hundreds of dollars. Simon's version, which is still in the prototype stage, would likely cost under a buck to manufacture.

And while regular earplugs are also cheap, they dampen all sound, can be an annoyance and are often forgone in the field, hearing loss researchers say. Service members need to be able to hear what's going on around them to detect danger and talk with each other and local residents.

"The idea was, we needed something that in the event of the unforeseen — an explosion, an IED that goes off near them — they needed to have something in place to protect them," Simon said.

He says the concept for the ABLE plugs came to him a little more than a year ago.

He had been listening to a radio report about hearing damage in those fighting overseas, and the story was on his mind as he stepped outside his Carroll County home to mow the lawn. He reached down to press the mower's primer bulb, and the idea of a check valve, which allows liquid or gas to flow one way only, popped into his head.

"It was that little spark moment," he said, "I thought, 'Ah ... if I could make something like [that] for your ear, it could prevent injuries like you're seeing over there."

Hearing impairments, often debilitating and permanent, have been the No. 1 service-connected disability reported among veterans since 2005, the Government Accountability Office reported in 2011. Tinnitus — a constant ringing in the ears — is the most common ailment, GAO reported, followed by hearing loss.

Benefit claims for hearing impairments have cost the Department of Veterans Affairs billions of dollars.

Nancy Macklin, a spokeswoman for the Hearing Loss Association of America, said veterans who have also lost limbs say that hearing loss is the "most troublesome" injury because it limits communication.

She said the group, headquartered in Bethesda, is reaching out to returning veterans to offer support.

Simon is hoping he can help military members avoid the loss altogether.

His a-ha moment at the lawn mower coincided with a call for Ignition Grant entries at the Applied Physics Lab. The grant program allows staffers to pitch ideas; the top proposals — as selected by other employees — win up to $20,000 in development funding.

Simon submitted his earplug plan.

"I thought, 'Well, it's a crazy idea, I haven't really thought it through that much, but let's put it out there and see how the APL community reacts,'" he said. "This is either really clever... or it's idiotic and I'm going to get shot down real fast."

It was a hit. Other smart people from across the lab added their two cents, Simon said, and soon he had several partners and the funds to create the prototype.

The ABLE crew has been testing the plugs at a facility on the lab campus, using a device that mimics the effects of an explosion. So far, Simon said, the earplugs have been shown to allow normal hearing pre-blast and to reduce pressure inside the ear by a factor of five or six post-blast. That's still not quite as good as traditional earplugs, but he's working on it.

"That's the bar that we're aiming to hit, to be just as good as traditional hearing protection," Simon said.

The biggest challenge was getting the right material for the poppet, which started out as a polystyrene ball until the engineers realized that the blast shot a pin-prick-thick hole right through the tiny sphere.

The creators debuted the plugs at an event last month sponsored by the lab and the Howard County Economic Development Association. The entities have entered into a technology-transfer partnership meant to help bring lab inventions to the marketplace.

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