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Weird audio experience

Discussion in 'Electronic Basics' started by [email protected], Oct 25, 2005.

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  1. Guest

    Hi all,

    Sorry for the crossposting, but I didn't quite know where to send this.
    I had a weird experience yesterday and I was wondering if this is
    physically possible or if a few screws temporarily got loose in my
    head.

    I'm presently learning Spanish with the use of a book and a set of 4
    CDs that come with it. I listen to the CDs using my computer, a small
    set of speakers, and a headset I plug into one of the speakers. In
    between oral exercises, I stop the CD and read the book while keeping
    on my headset until the next oral exercise.

    So yesterday, I had stopped the CD and was reading stuff in the book,
    and all of a sudden, I start hearing something that seemed like a
    conversation between 2 people in my headset, like on a CB radio or
    something. Of course, my computer was on but I wasn't connected to the
    Internet. So I was wondering, can there be radio waves roaming though
    my apartment (in case it can be useful, I'm surrounded by neighbours
    upstairs, downstairs and on either side of 2 walls of my apartment)
    which were caught by my headset?

    Viviane
     
  2. Charles

    Charles Guest


    Quite likely. Probably local, fairly strong. could be a bad
    connection in your audio setup detecting the radio waves, or an
    overload in an amplifier.

    It can be annoying if not wanted, but otherwise harmless.

    It could be an older cordless telephone, people don't realize they
    broadcast conversations. Newer ones use different frequencies and
    modulation, less likely to be picked up accidentally. Baby monitors
    can be a culprit as well.
     
  3. Androcles

    Androcles Guest

    | Hi all,
    |
    | Sorry for the crossposting, but I didn't quite know where to send
    this.
    | I had a weird experience yesterday and I was wondering if this is
    | physically possible or if a few screws temporarily got loose in my
    | head.
    |
    | I'm presently learning Spanish with the use of a book and a set of 4
    | CDs that come with it. I listen to the CDs using my computer, a small
    | set of speakers, and a headset I plug into one of the speakers. In
    | between oral exercises, I stop the CD and read the book while keeping
    | on my headset until the next oral exercise.
    |
    | So yesterday, I had stopped the CD and was reading stuff in the book,
    | and all of a sudden, I start hearing something that seemed like a
    | conversation between 2 people in my headset, like on a CB radio or
    | something. Of course, my computer was on but I wasn't connected to the
    | Internet. So I was wondering, can there be radio waves roaming though
    | my apartment (in case it can be useful, I'm surrounded by neighbours
    | upstairs, downstairs and on either side of 2 walls of my apartment)
    | which were caught by my headset?

    If your cell phone works in your apartment, then there HAS TO BE
    radio waves roaming though, right?
    Try placing your cell phone near your monitor.
    Androcles.




    | Viviane
    |
     
  4. CWatters

    CWatters Guest

    Quite possible.
     
  5. John Larkin

    John Larkin Guest


    Cheap audio gear, especially the RatShack stuff, can rectify and
    amplify strong radio signals. In our house, near a bunch of radio and
    TV transmitters, Shack amplified speakers and telephones both tend to
    pick up stuff. Radio stations are pretty obvious; a 60-Hz or
    high-pitch hum may be a TV station; a one-sided conversation is
    probably a ham radio operator; a 2-side conversation is likely AM
    walkie-talkies or wireless intercoms something similar.

    The speakers I have here make a sorta loud buzz when the volume
    control is set to *minimum*; turn it up just a bit and it goes away
    (there is actually a good reason for this!). I bundled all the wires
    together with twist-ties and it mostly went away (ditto.)

    The blue LED died too... the Shack sells some real junk!

    John
     
  6. Randy Poe

    Randy Poe Guest

    Not to get you paranoid, but there are radio (and TV and
    electromagnetic) waves not only in your apartment, but
    pretty much everywhere these days. Your FM radio wouldn't
    work unless the signal from all those stations was already
    present in your apartment, nor would your cell phone.
    Don't get too worried, though, as most of these signals
    are extremely weak and have to be amplified inside the
    electronic equipment in order to be useful.

    Hearing an AM radio station isn't unusual at all, as lots
    of things can act as simple AM decoders (see below). You
    were hearing something a little more unusual in that it
    was a 2-way conversation. Most cell phones are encrypted
    and wouldn't make audible conversation when picked up
    by a random unintended bit of wiring. I think wireless
    phones are FM and also not likely to be picked up this
    way. So as John Larkin suggests, perhaps it was an AM
    walkie-talkie or a wireless intercom in a nearby apartment.

    Intercoms and baby monitors have a pretty decent range.
    We used to listen to our baby monitor in the basement
    of our neighbor's house next door.
    Some years back I remember an article in the Washington Post
    about how people living in apartments near the WTOP-AM
    transmitter tower would get WTOP from their *walls*.
    It's a very powerful transmitter in a highly developed
    area, and apparently the metal stud construction of the
    apartment walls was a reasonably good broadband AM radio.

    I lived several miles away at the time, and it was common
    to hear WTOP in the background of phone conversations or
    in poorly grounded audio equipment.

    - Randy
     
  7. PD

    PD Guest

    You are swimming in a sea of electromagnetic waves, recoiling off of
    objects in the room and interfering with each other. This includes 60
    Hz waves from all your electrical wiring, radio waves, short waves,
    cell phone waves, television waves, infrared waves, even gamma rays.

    The ability of a receiver to amplify one of those and make them audible
    to you simply has to do with whether it is "tuned" to amplify that
    particular narrow band of frequencies.

    Feynman remarked about this in a wonderful TV interview. He said that
    electromagnetic radiation is like sitting in the corner of a swimming
    pool, with the splashing of children sending ripples everywhere and in
    all directions, bouncing off the walls of the pool and passing through
    each other and making general chaos in the water. And then it is quite
    remarkable to think that one could sit in the corner of the pool and be
    sensitive only to the rises and falls of the water as they lap up
    against you, and somehow make sense of that mess to be able to tell
    where the children are and what they are doing, for that is precisely
    what we do when we "see" the electromagnetic radiation in the visible
    light realm.

    PD
     
  8. Guest

    Thank you all for your knowledgeable explanations.
    I don't own a cell phone so it has nothing to do with what happened,
    but at least now I know that it wasn't just me being tired or
    something.

    Thanks again.

    Viviane
     
  9. kell

    kell Guest

    This story reminded me of an experience many years ago in Bellingham,
    Washington. As I sat playing guitar in my living room, someone started
    talking to me through the big stereo speakers sitting there, and
    commented about how well he could hear my guitar playing. I spoke back
    and we had a very intelligible conversation -- high audio quality with
    good volume. I don't think he told me what carried his end of the
    conversation.
    Later that day I walked into a store with hi-fis and stuff, and all the
    sound from the speakers died right at that moment. I didn't notice it
    because it happened just as I walked in from the street, but the clerk
    mentioned it.
    This happened in the seventies.
     
  10. Jasen Betts

    Jasen Betts Guest

    The headset cable picks up the radio waves and they travel back into the
    soundcard where they interact with the amplifier circuitry whic then
    produces the signals that go back up the leads and you hear them.

    It probably was CB and probably quite close.

    Bye.
    Jasen
     
  11. Years and years ago, a neighbor insisted that they
    sometimes heard Radio Moscow on their phonograph
    (which had no included radio, let alone short-wave).
    I sort of nodded indulgently, but one evening the man
    came over and said "I can hear it now!", so I went
    over. With no record playing (just its amp running),
    indeed I heard fragments of an English-language broadcast
    followed by a Radio Moscow station announcement. THis
    in the northeast of the US.

    Another time I was watching the 11:00 PM news on
    TV broadcast channel 2. The signal was for several
    minute overwhelmed by a St Louis, MO TV station
    long enough to get the location.

    Radio propagation and inadvertent demodulation in
    electronics can sometimes be quite weird.

    Dennis
     
  12. Even *normal* radio signals with *intended* demodulation can be quite weird sometimes.
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