Dental filling radio reception?

It's still speculated... see:

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I don't have any idea how it'd work, much less how the signal would be demodulated... However, I'd like to play devil's advocate and point out a few things... first is that tissue does not make a good faraday cage. You are a better conductor than rubber, but MUCH worse than copper. UHF and VHF passes through you relatively easily.

Secondly, do you want to assume that, if this legend is true, the filling induces sound in the mouth? Electrical impulses transmitted around your auditory nerve definately seem like sound to the beholder. Maybe that's the mechanism...?

Lastly, who's to say the filling acts as an antenna, a diode, or a battery? A filling in a saline solution, surrounded by nerves, bone, and other tissue might act completely differently than it would stand-alone.

I dunno if it's true or not... it'd be interesting to get concrete proof.

Dave

Reply to
dave.harper
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I didn't see the show, but the antenna efficiency for this sort of thing is extremely low. You would have to sit beside the transmitting antenna to have a chance of it happening.

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John Popelish
Reply to
John Popelish

Lucille Ball told a story on "The Dick Cavett Show" about picking up morse on her fillings after a trip to the dentist. She claims that she was driving by a big short wave transmitter. There is also a claim that she captured a Japanese spy during WWII with it...

When I was a kid, I used to hear morse late at night. I had several large fillings. My guess is that a neighbor had a big shortwave transmitter, and used it at night. I don't know morse, so it may have been an auditory hallucination, but it was repeated at least a few times, and, well, it really sounded like morse. Very spooky.

One theory is that is amalgam in fillings creates a diode. The strong wave rolling across it creates electrical impulses, which trick the auditory system (which is about a cm away, through that conductive media you were referring to) into believing there was sound. It probably only works for big fillings on the uppers, far back in the mouth, and then only with certain shapes and depth of filling, and formulas of amalgam.

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   Robert Monsen
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Reply to
Robert Monsen

Aluminum foil gum wrappers against amalgam filling might also rectify a bit.

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John Popelish
Reply to
John Popelish

Hi, everyone.

For years I've heard vague stories about people receiving radio broadcasts through their dental work. The stories have all the characteristics of a classic urban legend, and I'm pretty sure that's exactly what they are. Although I have no doubt that some people *think* they are hearing radio broadcasts, I believe that if proper tests would have been conducted it could have been shown that these were really mild auditory hallucinations.

So my question here has to do with the pure physics of a supposed dental radio receiver. The proponents usually do some hand-waving about the possibility of a diode forming in connection with a metallic filling or bridgework. The possibility seems at least plausible (any thoughts on that?), but they never seem to follow it any further. OK, so what is this diode going to connect to? How is the signal going to get transduced into sound? Etc, etc.

But the real show-stopper, I think, would be the fact that the whole "radio" is inside the mouth, surrounded by conductive tissue with no antenna protruding... a pretty good Faraday cage, I reckon. (Or maybe the radio only works when you stick out your toungue...!)

So the question is just how good of an RF shield is conductive tissue at normal AM or FM frequencies? Anyone have any data, or know how to compute it if we come up with some estimates for tissue conductivity and thickness?

Thanks!

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

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Reply to
Bob Masta

You need to catch the re-run of Myth Busters where they tested this very thing. IIRC (because I really wasn't paying a whole lot of attention) their conclusion was that it was plausible but not very likely (someone chime in if I'm wrong).

-- Best regards, Mark Daughtry, SR It takes "BALLS" to shoot a muzzleloader.

Reply to
M.Daughtry

Sit beside the transmitter, chewing on a mouth full of OA91 germanium diodes.

Reply to
Andrew Holme

BTDT. The galvanic current going through the root keeps you way too busy getting rid of it to bother listening for radio emissions.

- YD.

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Reply to
YD

Any idea where to get numbers to put on this? I'm especially interested in AM frequencies, simply because AM broadcasts can be easily detected, as in a crystal radio. But figures for the other bands would certainly be of interest.

Electrical pulses transmitted directly to your auditory nerve, as in an auditory prosthesis (cochlear implant) sound like buzzing. In order to get any semblance of the original sound you need a carefully orchestrated stimulation of multiple frequency regions. This is a really difficult task, with a lot of good people working hard on it. The problem is that the ear is not at all like a radio or telephone. It's a parallel device, with all frequencies analyzed while still acoustic, and transmitted as thousands of discrete frequencies on individual auditory nerve fibers. Each fiber's firing rate corresponds to the intensity of the particular frequency of the corresponding sensory cell. There is no place in the system where you can insert an electrical audio signal and have it interpreted by the brain as the original sound. (Unless perhaps your signal was a buzzer!)

Yes, my expectation is that if there is any diode junction at all, it's between metal and an electrolyte.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

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Reply to
Bob Masta

Not dental, but a friend of mine claimed he once heard a radio station over a flashlight. This happened back in the 1970s and he said he'd go into the kitchen late at night for a snack, and in the dead quiet darkness he could barely hear someone talking. Very strange; he didn't believe in ghosts but it took him a while to find where the voices were coming from: a flashlight held onto the side of the fridge by a magnet.

He didn't say what he did with the flashlight, as this was many years ago, but it would be interesting to dissect it today and see what was causing it. Perphaps some battery acid was acting as a rectifier between a battery terminal and a big spring. Once he had satisfied himself as to the source, he said he just left the flashlight alone and let it freak out his relatives who thought the kitchen was haunted.

My father told me he once heard a story of someone claiming to hear a radio station in her kitchen oven. This was the old convection oven, the kind built into the wall. He said it probably had something to do with old grease and other food-related crud building up against some metal contacts inside the oven.

I remember when I was a kid, picking up WBAP-820 AM radio very clearly over my little 3" reel-to-reel tape recorder speaker whenever I touched my finger to the terminals of the playback head. I guess my body was acting like a capacitor/antenna. WBAP is a big powerhouse and at the time I lived in the same city (Fort Worth).

Reply to
Matt J. McCullar

You

Not off the top of my head. Some mil-standards/specs might have that information. The statement "the body is a good conductor" can be true or false, depending on what you're using as reference. It's a great conductor compared to rubber, concrete, etc. It's an extremely poor conductor compared to copper, gold, even lead.

I'm guessing that microwaves and x-ray machines would be worthless if meat was a good conductor.

beholder.

That statement is incorrect. If cochlear implants only sounded like buzzing, then people wouldn't have them implanted. I think you're refering to the lower quality of the sound compared to natural hearing? Perhaps this quote could help:

"The sounds heard through an implant are different from the normal hearing sounds, and have been described as artificial or "robotlike." This is because the implant's handful of electrodes cannot hope to match the complexity of a person's 15,000 hair cells."

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Multiple frequencies you mean? Sound can be a single frequency or a superposition of many.

I don't believe that's a correct statement. If it was solely dependant on frequency, then you couldn't tell the difference between a 50Hz square wave, a 50Hz sine wave, or a 50Hz tuba note.

Just because everyday sound usually has many different origins operating at different frequencies doesn't mean you can't hear a single noise at a single frequency.

Isn't that the "goal" of a cochlear implant? To simulate real-world noise in the auditory nerve? As stated above, just because the implant can't mimic the the hairs in your ear perfectly doesn't mean it can't be done. That's a current-day limitation, not a permanent one.

Dave

Reply to
dave.harper

The fact that the body is a good antenna for AM is one of the things that makes me think the mouth would make a good Faraday cage. It must be a pretty good conductor at those wavelengths. But I'd sure like to be able to put some numbers on it. How does one determine the degree of Faraday screening, given the conductance (or whatever) of the screening material?

Thanks!

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

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Reply to
Bob Masta

How about stuffing AM radio up your arse and checking whether you can still hear the audio from the radio station?

Or doing the same with your mouth.

Just an idea :)

SioL

Reply to
SioL

And it just so happens that your teeth are "tuned" perfectly to a local station?

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Danny
Reply to
Danny T

local

Well that's the really neat thing about AM demodulation, you don't have to have anything tuned. You only need a simple rectifier.

Reply to
Anthony Fremont

I don't understand - my stereo can tune into different AM stations! :-\

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Danny
Reply to
Danny T

have

:-\

That's because it is employing *selectivity*, in the front-end and in the IF section(s). The nature of AM broadcast signals make them very easy to convert directly to audio frequencies. An antenna, a diode, and a ground connection are all that is needed to demodulate a strong AM signal. A set of high impedance headphones across the diode will allow you to listen. Just like this:

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It's actually a bit more complex in that what really (as in the real world) constitutes an antenna and a ground can get kind of odd. ;-) If you want to do more complex things (like actually chose a station), you will need to use tuned circuits and active semiconductors to improve selectivity, sensitivity, output volume etc...

Reply to
Anthony Fremont

Its quite simple, take 10-20m of wire and spread it around, if possible to a tree. Make a simple detector with a shottky or germanium diode with smoothing cap, attach sensitive headphones to the output of detector and you've got AM radio.

It will pick up strongest local station, no tuning needed.

SioL

Reply to
SioL

tree.

It's true about learning something new every day! I've learnt a lot more from this group in the last few weeks though - think I'll stick around!! :-)

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Danny
Reply to
Danny T

Well, it helps if your teeth look like the pushbuttons on an old car radio... just bite down on the proper tooth! ;-)

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

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Reply to
Bob Masta

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