5 ms·

Nice article, but the diagram halfway down that shows the EM spectrum.... I'm scratching my head over why "Audio" is apparently now electromagnetism.

BatFastard 11y ago
I was thinking exactly the same thing. Did my professors skip over something in the electromagic classes?
jjoonathan 11y ago
Bet you a dollar that you've got an unmodulated electromagnetic audio signal not two feet from where you're sitting (if not stuck directly into your ears). More importantly: I think it's fair to assume that someone reading an EM spectrum has the knowledge to figure out what they mean.
- madaxe_again 11y ago
  I'm a physicist and I have absolutely no idea what you mean by an "electromagnetic audio signal". I think what you mean is an EM wave which happens to carry an amplitude-modulated audio signal , which is not an audio wave. Audio waves are compressional waves formed in a medium, and require a medium for transmission through, such as air, or rock, or water, or even interstellar gas. Electromagnetic waves require no medium, and are brought about by energy transference between electric and magnetic fields in free space.
  - jessriedel 11y ago
    > I have absolutely no idea what you mean by an "electromagnetic audio signal". I think what you mean is an EM wave which happens to carry an amplitude-modulated audio signal ...So you did know what they mean.
  - jjoonathan 11y ago
    > I'm a physicist Useless nitpicking gives us a bad name. Please stop.
aylons 11y ago
Audio signals may - and usually are - represented by EM waves. Do not confuse "audio signals" with "acoustic signals". The diagram is not only easy to understand, but also technically correct.
- noselasd 11y ago
  The same image appears on https://simple.wikipedia.org/wiki/Electromagnetic_spectrum https://simple.wikipedia.org/wiki/Electromagnetic_spectrum with the text: "NOTE: The AUDIO entry in this graphic is there for comparison only. Sound waves and light are two different things entirely." Imo still somewhat confusing. I've never heard anyone refer to something on the EM spectrum as audio before.
  - aylons 11y ago
    You went to the simple image wikipedia just to find a citation that agrees with you, while the english Wikipedia has a whole artcicle describing it in quite an opposite way: https://en.wikipedia.org/wiki/Audio_signal https://en.wikipedia.org/wiki/Audio_signal If it is confusing, is because you do not understand what a "signal" means. A signal is not the phenomenon itself, it is a representation of it. An audio signal is a signal that represents sound, but it is not sound itself. If it were, you would not need to call it a signal, it would be simply "sound". In a slightly different use of adjective, an acoustic signal is a signal (that may or not be audio, eg, ultrassound) that is carried by sound waves. Actually, it only gets confusing if you try to be pedantic, as GP did. Everyone knows what an audio signal in a EM chart.
- deleted 11y ago
  [deleted]
- hanoz 11y ago
  > The diagram is not only easy to understand, but also technically correct. It's not easy to understand and I still don't understand it. What is audio doing on this diagram?
  - 11y ago
leephillips 11y ago
Author here. "Audio" is there for reference. It never occurred to be that this would cause confusion, but you're not the only one to object to it.
gaur 11y ago
"Audio sideband" is a common term for AM or FM sidebands from dc to a few tens of kilohertz or a few hundred kilohertz. Not exactly the same as calling a 10-km wavelength EM wave an audio wave, though.

BatFastard 11y ago

I was thinking exactly the same thing. Did my professors skip over something in the electromagic classes?

jjoonathan 11y ago

Bet you a dollar that you've got an unmodulated electromagnetic audio signal not two feet from where you're sitting (if not stuck directly into your ears). More importantly: I think it's fair to assume that someone reading an EM spectrum has the knowledge to figure out what they mean.

madaxe_again 11y ago
I'm a physicist and I have absolutely no idea what you mean by an "electromagnetic audio signal". I think what you mean is an EM wave which happens to carry an amplitude-modulated audio signal , which is not an audio wave. Audio waves are compressional waves formed in a medium, and require a medium for transmission through, such as air, or rock, or water, or even interstellar gas. Electromagnetic waves require no medium, and are brought about by energy transference between electric and magnetic fields in free space.
- jessriedel 11y ago
  > I have absolutely no idea what you mean by an "electromagnetic audio signal". I think what you mean is an EM wave which happens to carry an amplitude-modulated audio signal ...So you did know what they mean.
- jjoonathan 11y ago
  > I'm a physicist Useless nitpicking gives us a bad name. Please stop.

aylons 11y ago

Audio signals may - and usually are - represented by EM waves. Do not confuse "audio signals" with "acoustic signals". The diagram is not only easy to understand, but also technically correct.

noselasd 11y ago
The same image appears on https://simple.wikipedia.org/wiki/Electromagnetic_spectrum https://simple.wikipedia.org/wiki/Electromagnetic_spectrum with the text: "NOTE: The AUDIO entry in this graphic is there for comparison only. Sound waves and light are two different things entirely." Imo still somewhat confusing. I've never heard anyone refer to something on the EM spectrum as audio before.
- aylons 11y ago
  You went to the simple image wikipedia just to find a citation that agrees with you, while the english Wikipedia has a whole artcicle describing it in quite an opposite way: https://en.wikipedia.org/wiki/Audio_signal https://en.wikipedia.org/wiki/Audio_signal If it is confusing, is because you do not understand what a "signal" means. A signal is not the phenomenon itself, it is a representation of it. An audio signal is a signal that represents sound, but it is not sound itself. If it were, you would not need to call it a signal, it would be simply "sound". In a slightly different use of adjective, an acoustic signal is a signal (that may or not be audio, eg, ultrassound) that is carried by sound waves. Actually, it only gets confusing if you try to be pedantic, as GP did. Everyone knows what an audio signal in a EM chart.
deleted 11y ago
[deleted]
hanoz 11y ago
> The diagram is not only easy to understand, but also technically correct. It's not easy to understand and I still don't understand it. What is audio doing on this diagram?
- 11y ago

leephillips 11y ago

Author here. "Audio" is there for reference. It never occurred to be that this would cause confusion, but you're not the only one to object to it.

gaur 11y ago

"Audio sideband" is a common term for AM or FM sidebands from dc to a few tens of kilohertz or a few hundred kilohertz. Not exactly the same as calling a 10-km wavelength EM wave an audio wave, though.