Covert earpiece
November 1, 2010 8:22 PM   Subscribe

Where can I get a radio small enough to fit into my ear and be invisible so I can listen to information

I want a radio or something like it that can fit in my ear so I can listen to information. I have a product like this that uses an around-the-neck induction loop. The induction loop transmits to a small earpiece. Unfortunately, the earpiece is powered by two nine-volt batteries that run down pretty quickly.

Here is a list of other problems:
1. The signal is very quiet
2. I don't like the idea of a strong electromagnetic field on my body at all times
3. The induction coil can sometimes send the signal to phones (others can hear the information)
4. I don't like the tiny magnet sitting deep in my ear up against my eardrum

So what I want is something basically invisible that I don't have to fit under my clothes, doesn't look suspicious, and can transmit information to an earpiece at a reasonable volume

Some ideas:
1. A tiny AM radio with a box that sends a very strong signal to it.
2. A tiny speaker that fits in my ear and receives signals from a small briefcase outfitted with a large power source and a large coil (I am thinking something like a large, powered amplifier connected to a speaker that has its magnet and diaphragm removed.)
3. A very small FM radio.
4. An extremely small bluetooth radio.
5. Ultrasound waves that transform from un-hearable to hearable when they hit my body.

Some of you may be wondering what I use this for. I basically use this to learn anything and everything. I listen to books all day. They are transformed from text into MP3 files using the mac automator. Then, I listen to them.

I DO listen responsibly. I don't listen at work. I also don't listen while driving or operating any heavy machinery, or doing dangerous tasks.
posted by candasartan to Science & Nature (9 answers total) 6 users marked this as a favorite
Would a Bluetooth earpiece be "covert" enough, and would you be ok with only one ear? If so, you can pipe your audio source of choice to a standard Bluetooth earpiece. It would obvious you were wearing it, but a Bluetooth earpiece doesn't have the same "I am listening to something and tuning you out" connotation that you'd get with earbuds/headphones.

Now that I re-read the question, I see you've considered Bluetooth but (apparently) don't consider the typical products to meet your needs. Exactly how invisible a device are you looking for? Is it ok if it's visible but mistakable for something else, like sunglasses or a hearing aid? Is your hair long enough to conceal some electronics, or would you consider growing it out for this project?
posted by contraption at 8:38 PM on November 1, 2010

"Invisible Earpiece" found some good results for me. It also found some things that remind me of the back of an issue of Popular Science. I would try to find a Bluetooth unit as well.
posted by UsernameGenerator at 8:46 PM on November 1, 2010

Here's an RF-based system that's probably similar in appearance to your induction-loop prompter rig. I didn't see any pricing information but I'm sure it wouldn't be cheap.

You've probably thought about this already, but are you really sure having a secret agent covert earpiece is the best way to achieve your goal of listening to audiobooks all day? I could see it being fun, maybe, but it seems impractical for long-term use.
posted by contraption at 8:50 PM on November 1, 2010

Each design constraint you add reduces the solution space.

What that means is that you want a function, and you want it to be:

Perfectly safe
Power Miserly
Available off the shelf
Undetectable by emissions/interference
Stand-alone (i.e., no wires)

Might just want to add to this:

Speaks to the dead
Turns lead into gold
Finds the fountain of youth
Makes girls swoon

I know of nothing like this, but for $20,000 or so, I'll work on the first section and see what I can do. That should cover supplies and a few months of work.

Hearing aids are your best bet, modified to receive only ultrasonics or radio. They are already designed to meet most of your specs, and are reasonably power miserly. An FM radio receiver can be added to one, but discriminator magnetics rule out the tiny. An AM radio is only a diode, cap, and speaker/earbud, but at this level of simplicity, is subject to random AM fields, which means anything making a spark almost. Volume is an issue, since a battery-free unit would require a little antenna wire, but this could wrap around your ear inconspicuously enough.

Perhaps you could do this with infrared-light, modulated with your audio source and detected with a suitable IR filter and detector. Photo-diodes are pretty cheap, some are already equipped with IR filters, and they would fit in an ear hole. (It would help to drill out the ear hole to 1/2", of course, but if that's out, a behind the ear optical receiver might fit the bill nicely.) Light is electromagnetic, but modulated IR can be pretty economic, as you will note from your TV remote control.

Roll your own might be as cheap as a purchased solution, but the optimum solution may involve compromises to your constraint list. That's how real world design works.

The other thing is that real-world designs usually exist because there is a demand large enough to amortize the effort required over a very large number of units. When the unit count is 1, you get 100% of the non-recurring costs rolled into the price tag. If you got 1000 people to share in the development costs, it would only be $20 per ear piece, plus the recurring costs of the device, provided I am in the ballpark with my $20k guess.

Behind the ear optical is do-able in a custom form. I think it would meet many of your requirements.
posted by FauxScot at 12:21 AM on November 2, 2010 [2 favorites]

One more thing... if you are female (or a metrosexual) and OK with large ear-rings, there's a packaging option to explore. A quarter sized lithium thional chloride 3.6V button cell would last quite a while as a dongle hanging from a lobe, and solve a whole lot of real estate issues. Just a thought. A lame ass thought, but a thought. 3 Volt lithium cells could probably last a few days to many days, too, but with 1/2 the capacity. I'm not sure Tadiran makes button cells in lithium thional chloride technology, but I'll bet they do.

Another option is a behind the ear MP3 player, repackaged from parts extracted from an iPod or made from readily available parts. This actually might be better, since you are going to use it to play back audio anyway. Once you compromise on behind-the-ear, you have enough volume in the package to do a lot of stuff that in-the-ear might not allow so easily.
posted by FauxScot at 12:30 AM on November 2, 2010

FauxScot: To be fair, I don't see the OP mentioning a price constraint (though one may exist).

What is the battery life requirement? How long are the current batteries lasting?
posted by RikiTikiTavi at 9:06 AM on November 2, 2010 [1 favorite]

Oh, and you say the earpiece is powered by two 9-volt batteries? Your existing earpiece must be HUGE, then. What size is acceptable?

There are hearing aids like this that are driven via FM. Don't know if the form factor is covert enough. A plus is that the bands it uses aren't US broadcast radio. Same issue is a minus, though, since you probably have to buy their transmitter.
posted by RikiTikiTavi at 9:24 AM on November 2, 2010

> Oh, and you say the earpiece is powered by two 9-volt batteries? Your existing earpiece must be HUGE, then. What size is acceptable?

The OP says their current earpiece uses an induction loop like the units here. The 9V batteries are presumably powering the loop which goes around the wearer's neck and which sets up a field to vibrate the magnet in the earpiece.

OP: As FauxScot explained, the constraints you've specified limit you to expensive devices designed for public speakers and law enforcement, and even then the battery requirements will probably not be what you're hoping for. It would be really helpful to know exactly what the situation is so that we can try to come up with solutions that may not fit your list exactly, but that find alternate ways around one part of the problem or another. I've been trying to imagine a scenario where all the things you've listed would be necessary, but frankly I'm drawing a blank unless you're trying to cheat on exams or tune out lectures or meetings where your attendance is required.
posted by contraption at 10:21 AM on November 2, 2010

The more I think about this, the more light sounds like a good idea. I've gotten some infrared links to work over scores of feet.

Might adjust my estimate downwards. A small photodiode and some IR filter material. I think it could be highly miniaturized... but really big ears would be helpful. Again, power is a limiting factor. If you'd be willing to pierce your ears to allow feed-through connections, that would allow a behind the ear battery pack and address most of the issues of concealability and battery life. Would be a neat body hack that might get you on the front page of Digg or something. Woot.
posted by FauxScot at 11:08 AM on November 2, 2010

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