Hearing Aid in the Microwave
Question:
My Uncle Al took his hearing aid out and laid it on the coffee
table and his dog, named Junior, came along and took it in his
mouth, assuming it was a morsel of cookie. The dog, being an
expert on cookies, quickly dropped it,
but not before it was soaked with dog spit. Al banished Junior to
the bathroom and thought he would dry out the hearing aid by
placing it in his microwave oven for a couple minutes. It doesn't work now. Do you think the microwave
might have damaged it?
Answer:
Placing delicate electronic equipment in a microwave oven is an
"enterprise fraught with hazard", as Father said about
jumping out of a perfectly good airplane when I told him about
skydiving.
A microwave oven works by subjecting its contents to an
intense electromagnetic field which changes direction about 5000
million time a second. This is real handy for cooking food since
food has significant water content and water molecules have a
positive electrical charge on one end and a negative electrical
charge on the other. The alternating electric field shakes the
water molecules back and forth, imparting energy which shows up
as heat.
Material which does not contain much water and does not
conduct electricity, like air and crockery, is pretty much
unaffected by microwaves. Electrical conductors appear to reflect
microwaves because the electric field of the wave induces
electrical currents to flow in the conductor. These internal
currents alternate at the same frequency as the incoming wave and
re-radiate a wave that looks like the original. Semiconductors
also have electrical currents induced in them by the incident
wave. Because semiconductors have higher electrical resistance
than do conductors, the internal currents generate considerable
heat.
A hearing aid is a collection of
insulators, conductors and semiconductors. Subjecting one to
microwaves is very likely to cause electrical currents and heat
sufficient to destroy the semiconductors and generally cause
arcing and sparking around the inside of the device. I would
recommend that if your dog takes your hearing aid in his mouth
and later gives it back, which by the way is only one
possibility, take the battery out of it, rinse it off in clean
water and set it in a dry warm place for a day or so to dry. That
might restore it...or perhaps not.