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Dental filling radio reception?

Discussion in 'Electronic Basics' started by Bob Masta, Jan 6, 2005.

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  1. Bob Masta

    Bob Masta Guest

    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

    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?


    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
  2. M.Daughtry

    M.Daughtry Guest

    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).
  3. 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.
  4. Guest

    It's still speculated... see:

    I don't have any idea how it'd work, much less how the signal would be
    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

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

  5. Andrew Holme

    Andrew Holme Guest

    Sit beside the transmitter, chewing on a mouth full of OA91 germanium
  6. Aluminum foil gum wrappers against amalgam filling might also rectify
    a bit.
  7. Hi,

    Then there's getting speech or music out of the gas stove.
    That is a little more plausible as I seem to recall that a flame
    can be used as an RF detector.

    I once got a stream of water out of my electric wall socket
    but that was just the folks upstairs leaving a water tap on and
    then going on holiday.

    Cheers - Joe
  8. Ok, here's one for ya....

    I was about 12 at the time. We had gone away for a couple hours - my mother,
    younger brother and myself. We merely went to the store to pick up a couple
    things, a total of 10 miles round trip. My Dad and I believe one other
    person was at home. There was a hail storm came through that day and lasted
    about 15 minutes. The house had a basement, 1st floor and 2nd floor. The
    first floor in the kitchen - the dome which hung from the kitchen ceiling
    lamp had hail and water in it. There was NO leaks in the roof, no leaks
    evident in the bedroom above the kitchen. No way we could think of, for the
    water/hail to have gotten in that dome. While I'm sure there must be some
    reasonable explanation for it, it sure defied one and still does - at least
    to the writing of this. That was the first and last we noticed that sort of
    thing - in our time there.

  9. Maybe Jesus put it there...or your little brother.
  10. Nah, don't think so...... Little brother couldn't reach it and beside, he
    was with us! Jesus - well, to each his own - but I don't think such a
    person/entity would waste their time doing stupid tricks like that. Try

    The Shadow
  11. Hmmmmm. Yeah, maybe.

  12. Batman?
  13. Don Bruder

    Don Bruder Guest

    More interesting is using a flame as a speaker.

    Yes, this one's actually for real, and *INCREDIBLY* effective. Once
    things are set up and adjusted properly, it can be tweaked to produce
    enough volume to practically blow you into the next county. I don't
    claim full understanding of the workings, but I've seen it in action,
    and I was *VERY* impressed, both with the quality and quantity of sound
    output. A propane flame that looked to be about 10 inches tall from my
    vantage point in the bleachers was WAY more than adequate for use as a
    PA speaker at the county fairgrounds where the demonstration was done,
    and was reported to be heard, clearly enough to be intelligble, more
    than a mile away.

    Of course, the heat that came as a by-product, and the clear space
    required to prevent it from being a fire hazard, was something of a
    downside. (The demo was set up in the infield of the harness-racing
  14. 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.

    Robert Monsen

    "Your Highness, I have no need of this hypothesis."
    - Pierre Laplace (1749-1827), to Napoleon,
    on why his works on celestial mechanics make no mention of God.
  15. YD

    YD Guest

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

    - YD.
  16. Bob Masta

    Bob Masta Guest

    On 6 Jan 2005 08:53:53 -0800, wrote:

    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

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
  17. 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).
  18. Bob Masta

    Bob Masta Guest

    On Sat, 08 Jan 2005 15:16:08 GMT, "Matt J. McCullar"
    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?


    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
  19. Guest

    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.
    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."
    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.

  20. SioL

    SioL Guest

    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 :)

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