Static Electricity
can play havoc with cochlear implants
Plastic playground slides can zap hearing
devices and force kids to play in silence
As reported by Eric Hand
St. Louis Post-Dispatch
Six-year-old Taylor Zinderski slid down a plastic slide
and slipped into silence.
It was October at a church
playground. Taylor, deaf for almost two years, ran to her father. She
told him her cochlear implant -- an electronic device that lets her
hear -- had suddenly fizzled.
It had been zapped by a static electric shock. Chris Zinderski hadn't
switched off his daughter's implant because he didn't believe that static
could really be a problem.
"Now I've learned my lesson," he said.
Plastic slides studied
The shock didn't ruin
Taylor's implant, but it did require an inconvenient trip to an audiologist.
Static electricity is so much of a worry and hassle for the deaf that
Washington University electrical engineer Robert Morley has a grant
to study one of its main sources: plastic playground slides.
As playground slides evolve from metal to durable, cheap and colorful
PVC plastic, deaf children face a sad choice: Don't play, or turn off
their implants and play without sound.
Some playgrounds, such as new "all inclusive" ones, have deliberately
included metal slides, which don't produce static electricity. But many
others don't -- including some that are supposed to be accessible to
disabled children.
"Every time I look, there's another we can't go to," said
Peg Jones, the mainstream coordinator at St. Joseph Institute for the
Deaf in Chesterfield, Mo.
In the name of science
Morley, who helped pioneer
digital hearing aids, got a small federal grant to study the issue.
His first task: See how much static a slide can make. He sent his two
daughters down St. Louis-area plastic slides hundreds of times, wearing
different clothes.
Static electricity occurs when a "positive" material sheds
electrons by rubbing a "negative" material that attracts them.
Good static-producing combinations include wool and PVC plastic, hair
and rubber, and skin and polyester. Cotton, paper and steel are neutral.
The resulting charge on both objects can dissipate slowly in humid air,
or cause a shock if it touches something that is grounded, such as a
person, a car -- or the metal pole that Morley had his daughters touch
after each slide.
Humidity is a factor
The type of clothes and
length of the slide didn't matter much. But humidity did. In the cold,
dry air of winter, Morley's daughters achieved charges of about 10,000
volts. Morley says that in the dry air of Tucson, Ariz., a colleague
measured 20,000 volts after a slide.
In coming months, he will apply those voltages to test implants, which
are rated to withstand 8,000 volts, according to Doug Miller, an engineer
with Cochlear Americas, one of the manufacturers of the devices.
Cochlear implants can cost more than $50,000. They require a delicate
surgery to insert a wire into the snail shell-shaped cochlea. A hearing
aid outside the ear picks up sound and converts it to an electrical
signal that is broadcast through the skin to the internal device, which
electrically stimulates the auditory nerve.
Miller and Morley both stress that static electricity is not a threat
to the internal part of the implant. It can only zap the external equipment
and force a trip to the audiologist for recalibration.
Miller says it will soon be a nonissue, as deaf people move to newer
implants that can withstand more static. New rules will require a rating
to 15,000 volts, and most companies test the devices at even higher
levels, he says.
Spray away the static
But until then, each room
at the Moog Center for Deaf Education in St. Louis County will keep
a bottle of diluted fabric softener for spraying down staticky kids
and carpets. On a cold November morning, family school director Betsy
Brooks watched for signs of static.At recess out on a wood and metal
playground, the children played with their implants turned on. Taylor
sailed down the metal slide, her mop of curly blond hair bouncing in
the air. Jones feels sorry for the children who have to turn their implants
off."It's a completely different experience to go down the slide
without the wind and the 'whee,' " she said.
January 2006
UPDATE:
Allowing the children to wear our new Static
Friendship Bracelet* may help this problem or make it become obsolete.
