When is a hearing aid not a hearing aid?

June 25, 2017 at 12:34:21
Specs: several
A few weeks after moving into a new apartment, I found a tiny
hearing aid stuck to the underside of the countertop microwave
oven which came with the apartment. I think the oven was placed
in the apartment by the property manager between the day I first
looked at the apartment and the day I moved in, because I don't
remember it being there before. I just mention that to explain why
it isn't obvious who the hearing aid belonged to. This apartment
may have been unoccupied for as long as five years, or possibly
even six, since spring of 2011 when an elderly couple lived here.

The hearing aid was stuck to the bottom of the microwave by
magnetism. There was also a nail and a screw stuck there. No,
the hearing aid was not nailed or screwed to the oven!

I quickly found that -- very surprisingly -- the magnetism was not in
the microwave (which of course contains a magnetron) -- but in the
hearing aid!

Printed on the hearing aid are the words "dot by ReSound". I looked
that up on this Internet thingy and found "dot2" way down at the end
of ReSound's list of "legacy" hearing aids. Apparently the original
"dot" is so old that they didn't even bother to list it. But it looks just
like the dot2, and images I find may be of the "dot". The one I have is
metallic magenta in color. That's the plastic case. The battery door
is black. An online image shows the battery held by the door with the
door swung open. The door snaps out of the one I have, and detaches
rather than swinging open. It snaps back in neatly, though, and does
not appear to be broken. That might be a design change, with the
hinge added to later models.

With the door removed, I see what appears to be the battery inside the
case. It does not come out with the door, and does not become loose
when I remove the door. There is no obstruction. It looks like I should
be able to lever it out with a toothpick or paperclip, but it doesn't budge.
It is wedged in very tight. Or it is held in with superglue. Which doesn't
make any sense for the electrical contacts.

The tiny button battery takes up less than half the volume of the tiny
compartment, and the rest of that compartment is empty! So about a
third of the whole volume is the case itself, almost third is the battery,
and at least a third is empty space around the battery. There is also a
bit of transluscent white or colorless plastic where the sound tube is
supposed to be, with a plug that goes into the ear, but the tube and
earplug are missing. Instead, where the beginning of the hollow tube
should be is solid plastic, apparently cut or broken off just beyond the
edge of the magenta case. The transluscent plastic is a rod instead
of a tube!

And the "battery" is the source of the magnetism. The flat ends of the
battery are the poles. It is moderately strong. It isn't a super-strong
magnet like some I've seen, but it is definitely no weakling. It just now
held a piece of steel that must weigh ten or twenty times as much as
the entire hearing aid. And that was through the side of the case.
Maybe I'm wrong about it not being super-strong.

The hearing aid case is shaped (and colored) sort of like a human
liver, 21 mm long, 10 mm wide near the middle, and 6 mm thick.
The "battery" is 3 mm thick and about 6 or 7 mm in diameter. It's
hard to measure inside the case without a proper measuring tool.

Any idea what's going on here?

Should I tear the case apart to get the "battery" out?

-- Jeff, in Minneapolis

message edited by Jeff Root

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June 25, 2017 at 12:46:14
I am a little surprised that even an older type of hearing aid would have strong magnet within it...

Perhaps I'm being a little "overly cautious" here... but I'd be inclined to ensure the device is - to put it mildly - disabled in a serious way... A hammer comes to mind.

Also perhaps have a good hunt about the property to ensure there aren't any other surprised lurking...

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June 25, 2017 at 13:13:38
I'm not *THAT* paranoid. Part of the mystery is why there
appear to be no innards to the hearing aid at all -- just the
"battery" and nothing else.

I'm not sure how old you think "older" is. It looks new to me,
but the list on the ReSound website suggests that it must be
about the right age to have gone obsolete about the time this
apartment was last used. The building was put up in 2000,
and the microwave was made in 2000. But as I said, the oven
may have been stored or in use in some other apartment.

Still, come to think of it, I suspect Fred, the maintenance man,
of being an evil genius. He may be clever enough to make it
look like just an innocent hearing aid left behind by a former
occupant. Diabolical!

On the other hand, if Fred wanted to bug the place, he's has a
million opportunities to plant them anywhere he wants. Behind
the baseboards, in the air ducts, in the electrical outlets....

-- Jeff, in Minneapolis

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June 27, 2017 at 05:01:46
I wear current version Resound hearing aids. The battery compartment is sized for an exact snug fit for the correct battery. My guess would be that the wrong battery is installed.

To my knowledge there aren't any magnets in hearing aids powerful enough to hold them in place to magnetic metals.

What you describe is an older version of a behind the ear unit. How do you know there is nothing inside the hearing aid besides to battery? The battery should fall out. If it doesn't fill the cavity then it is the wrong battery for that unit. Someone may have indeed glued it in there to keep it in place.

Metals that are magnetically attracted may actually become magnetic themselves when exposed to strong magnetic fields. The shell of the battery is made of steel, as is the nail, and probably the screw.

Why not ask your landlord about this? The hearing aid must have belonged to someone. Why would you find the need to tear out the battery?

Why not just stop at any hearing aid store and find out what you have.

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June 27, 2017 at 13:29:48
> How do you know there is nothing inside the hearing aid
> besides the battery?

As I said, the case is shaped sorta like a human liver. Roughly
triangular with unequal convex-curved legs and concave-curved
hypotenuse. The door takes up almost the entire hypotenuse.
The corner with the more acute angle (adjacent to the hypotenuse
and the longer leg), has the transluscent whitish plastic that should
be the start of the sound tube. When I remove the door, I can see
the cavity inside. What looks like a button battery -- a squat, silver
cylinder -- is in the center of the opening, apparently pushed into
the obtuse opposite corner of the case, with the entire rest of the
case visibly empty. There is at least as much empty total volume
on each side and in front of the battery as the battery occupies.
Something comes out of the back (inside) of what should be the
sound tube, but I can't make out what it is. I may have damaged it
in trying to pry the "battery" out.

The only weighing scale I have is crude. The hearing aid is too
light to register. I estimate that it is roughly the weight of a US dime
or penny. It easily magnetically holds a piece of steel reinforcing
bar which weighs about as much as 40 dimes, or roughly 4 ounces.
I suspect that if I were to remove the "battery" from the case, and
use a differently-shaped piece of steel, it might hold 80 times its
own weight.

Note that I'm not just saying the hearing aid sticks to the reinforcing
bar, I'm saying that the reinforcing bar hangs from the hearing aid,
and I have to tug on them to pull them apart.

I suspect that what looks exactly like a battery is actually just a
strong magnet. Either that or I know nothing at all about batteries.

I'd break the hearing aid case apart to get at the nifty magnet or
magic battery ... which probably loses its magic when removed
from the case.

-- Jeff, in Minneapolis

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June 27, 2017 at 20:37:03
Hearing aid batteries look just like a miniature CMOS batteries for a motherboard. The positive & negative sides look different.


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June 28, 2017 at 00:21:46
My parents both had hearing aids, and I found some used batteries
just now. They are slightly larger in both thickness and diameter than
the thing inside the ReSound case. 5 mm thick versus 3 mm, and
8 mm diameter versus 7 mm. I'm sure there are numerous different
sizes of hearing aid batteries.

You've given me a great idea. I can stick these old batteries under
the microwave oven and turn it on! I'll send this post first. If you
don't hear from me again, you can presume I did something wrong.

-- Jeff, in Minneapolis

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June 28, 2017 at 00:33:10
Care for some tea? I've got the boiling water.

I ran the microwave three times for one minute each,
putting a battery about where I found the hearing aid,
but the battery came away each time with no detectible

-- Jeff, in Minneapolis

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