4 ms·

Wow, can anyone explain this?

xwintermutex 11y ago
I guess it is because of the use of amplitude modulation [1], where the envelope ("strength") of the carrier (that is some higher frequency signal) follows the signal that is modulated onto it (speech, in this video). With say FM it wouldn't work, I presume. [1]: https://en.wikipedia.org/wiki/Amplitude_modulation https://en.wikipedia.org/wiki/Amplitude_modulation
- jimmaswell 11y ago
  If you listen to an FM signal interpreted as AM you can often still make out the audio, it'll just be very clipped and noisy. That was the result when I did this with an RTLSDR, at least
AndrewKemendo 11y ago
Same way as a plasma speaker https://www.youtube.com/watch?v=PJpn2PzhvP4 https://www.youtube.com/watch?v=PJpn2PzhvP4
- okbake 11y ago
  It would be cool to see a guitar amplifier that worked like this. It seems dangerous, but that would be awesome to hear/watch.
- JoshTriplett 11y ago
  Or, on a larger scale, a Zeusaphone/Thoremin: https://www.youtube.com/watch?v=3ff_AXVlo9U https://www.youtube.com/watch?v=3ff_AXVlo9U
- jakeogh 11y ago
  https://www.youtube.com/watch?v=hgll-XTqcS4 https://www.youtube.com/watch?v=hgll-XTqcS4 (youtube-dl with mpv fullscreen recommended)
  - icpmacdo 11y ago
    Dumb question is it also creating the piano like sound in that video with the electricity? Very cool to watch.
    - jakeogh 11y ago
      Yes! That's all done with the plasma channel expanding and (therefore) contracting at audible frequencies. (edit: I'm way wrong on the piano. arjie's correct about the backing track)
    - arjie 11y ago
      There's a backing track.
URSpider94 11y ago
The voltage applied to the cable is directly proportional to the audio signal, overlaid on a ~1 MHz carrier. All you need is a mechanism that transforms those voltages into vibrations or pressure waves. Presumably, since it seems to happen only when he's striking an arc, it's related to the local heating of the air in the gap ... But I guess it could be electromagnetically induced vibrations of the cable or the tower structure ... There used to be stories, not entirely urban legend, of people who lived close to AM towers hearing the station in the wiring of their home, or in their dental appliances. Not impossible, considering that many AM stations broadcast with 50kW of power (like the one in this video) and can be received across a large swath of the country.
- luxflux 11y ago
  There used to be stories, not entirely urban legend, of people who lived close to AM towers hearing the station in the wiring of their home, or in their dental appliances. Reminds me of a Gilligan's Island episode, Hi Fi Gilligan: https://www.youtube.com/watch?v=3x1XHv0sxro https://www.youtube.com/watch?v=3x1XHv0sxro
  - thwarted 11y ago
    Lucille Ball talking about picking up radio signals in her fillings. https://vimeo.com/72473069 https://vimeo.com/72473069
- paulgerhardt 11y ago
  That was one specific station - the infamous WLW / W8XO - the first and only US station authorized to operate at 500kW of power.[1] To give you an idea of how powerful that is, take a look at their coverage map: http://i.imgur.com/Aigz1Zh.jpg http://i.imgur.com/Aigz1Zh.jpg The back story is kind of interesting. It was run by Powel Crosley - a sort of 1930's version of Elon Musk. Advertising revenues from the station were so successful he applied to increase the limit from 500kW to 750kW(!). It's a big deal in the ham community, but I only learnt latter that while US stations were limited to 50kW - other parts of the world didn't have such restrictions. Parts of the Middle East have 2,000kW stations. [2] You can get a full download on the Crosley WLW station in this video: https://www.youtube.com/watch?v=CbHjcwIoTiY https://www.youtube.com/watch?v=CbHjcwIoTiY [1] http://www.ominous-valve.com/wlw.html http://www.ominous-valve.com/wlw.html [2] https://en.wikipedia.org/wiki/Transmitter_Solt https://en.wikipedia.org/wiki/Transmitter_Solt

I guess it is because of the use of amplitude modulation [1], where the envelope ("strength") of the carrier (that is some higher frequency signal) follows the signal that is modulated onto it (speech, in this video). With say FM it wouldn't work, I presume. [1]: https://en.wikipedia.org/wiki/Amplitude_modulation https://en.wikipedia.org/wiki/Amplitude_modulation

jimmaswell 11y ago
If you listen to an FM signal interpreted as AM you can often still make out the audio, it'll just be very clipped and noisy. That was the result when I did this with an RTLSDR, at least

AndrewKemendo 11y ago

Same way as a plasma speaker https://www.youtube.com/watch?v=PJpn2PzhvP4 https://www.youtube.com/watch?v=PJpn2PzhvP4

okbake 11y ago
It would be cool to see a guitar amplifier that worked like this. It seems dangerous, but that would be awesome to hear/watch.
JoshTriplett 11y ago
Or, on a larger scale, a Zeusaphone/Thoremin: https://www.youtube.com/watch?v=3ff_AXVlo9U https://www.youtube.com/watch?v=3ff_AXVlo9U
jakeogh 11y ago
https://www.youtube.com/watch?v=hgll-XTqcS4 https://www.youtube.com/watch?v=hgll-XTqcS4 (youtube-dl with mpv fullscreen recommended)
- icpmacdo 11y ago
  Dumb question is it also creating the piano like sound in that video with the electricity? Very cool to watch.
  - jakeogh 11y ago
    Yes! That's all done with the plasma channel expanding and (therefore) contracting at audible frequencies. (edit: I'm way wrong on the piano. arjie's correct about the backing track)
  - arjie 11y ago
    There's a backing track.

URSpider94 11y ago

The voltage applied to the cable is directly proportional to the audio signal, overlaid on a ~1 MHz carrier. All you need is a mechanism that transforms those voltages into vibrations or pressure waves. Presumably, since it seems to happen only when he's striking an arc, it's related to the local heating of the air in the gap ... But I guess it could be electromagnetically induced vibrations of the cable or the tower structure ... There used to be stories, not entirely urban legend, of people who lived close to AM towers hearing the station in the wiring of their home, or in their dental appliances. Not impossible, considering that many AM stations broadcast with 50kW of power (like the one in this video) and can be received across a large swath of the country.

luxflux 11y ago
There used to be stories, not entirely urban legend, of people who lived close to AM towers hearing the station in the wiring of their home, or in their dental appliances. Reminds me of a Gilligan's Island episode, Hi Fi Gilligan: https://www.youtube.com/watch?v=3x1XHv0sxro https://www.youtube.com/watch?v=3x1XHv0sxro
- thwarted 11y ago
  Lucille Ball talking about picking up radio signals in her fillings. https://vimeo.com/72473069 https://vimeo.com/72473069
paulgerhardt 11y ago
That was one specific station - the infamous WLW / W8XO - the first and only US station authorized to operate at 500kW of power.[1] To give you an idea of how powerful that is, take a look at their coverage map: http://i.imgur.com/Aigz1Zh.jpg http://i.imgur.com/Aigz1Zh.jpg The back story is kind of interesting. It was run by Powel Crosley - a sort of 1930's version of Elon Musk. Advertising revenues from the station were so successful he applied to increase the limit from 500kW to 750kW(!). It's a big deal in the ham community, but I only learnt latter that while US stations were limited to 50kW - other parts of the world didn't have such restrictions. Parts of the Middle East have 2,000kW stations. [2] You can get a full download on the Crosley WLW station in this video: https://www.youtube.com/watch?v=CbHjcwIoTiY https://www.youtube.com/watch?v=CbHjcwIoTiY [1] http://www.ominous-valve.com/wlw.html http://www.ominous-valve.com/wlw.html [2] https://en.wikipedia.org/wiki/Transmitter_Solt https://en.wikipedia.org/wiki/Transmitter_Solt