Simple question, or is it...


What exactly is an audio signal made of, and what exactly is the medium it travels through in a cable??
thecarpathian
Good question. When you find out let me know.

First approximation, its immaterial. I mean that literally. Its charges. Its all charges. Which gets to forces. Not things. Not really. Forces between things. Which in turn when broken down further are all forces. No kidding. That's literally the meaning of E=mc2. Energy, a force, equals mass, a thing. Times the speed of light squared. So you can say its a force or a charge, or you can say its a thing or a medium. It all depends on your point of view. On which side of the equals sign you want to take.

When you look at what holds things together, its all charges. At the atomic level there's the strong nuclear force that holds the neutrons and protons of the nucleus together. I'm sure you've always wondered why if like charges repel then what holds all those protons together? They should fly apart. And they would. Except for the strong nuclear force. Holds the nucleus together.

The strong nuclear force attenuates rapidly with distance so that it only applies within the nucleus. Beyond that, from atoms and molecules to cells and all the way up to people and wires its electrons and electromagnetic forces.

Just sitting there in your chair, what is it stops you melting right on through it? Ultimately it comes down to the electrons in your body and clothing being repelled by the electrons in the chair.

Okay, so obviously the same thing happens when you pull a bow across a string on a violin. That sets a whole slew of electrons to vibrating and away we go! Electrons in the air repel other electrons in a compression wave that reaches a microphone, which is a membrane that moves in analog with the air, and being attached to a transducer generates a signal in a wire.  

Up until now the "signal" which really is just another word for information has been propagating out in all directions. Now in the wire its a bit more constrained. But maybe not so constrained as you might think. The signal (information) is not all in the wire. Remember, its a force. Quite a lot of the signal is in fields that extend out beyond the wire in all directions.  

For the most part though its electrons in the wire pushing against neighboring electrons in the wire in a wave function that is a direct analog to the microphone and the air and the bow and the string that started it all. Like when you see people doing "the wave" at a game, the wave moves but the people stay put, more or less. Same with the electrons. More or less.

That's your signal. And that's your medium. Its all the same thing. Which isn't even a thing, but energy. Or mass. Take your pick.
@OP, 
I would wait for Almarg or Atmasphere to respond.
B
It’s an electromagnetic field.  
Read all about it:



https://en.m.wikipedia.org/wiki/Electromagnetic_field
After clicking on that link, I feel my previous post to be even more relevant.
B
mapmanIt’s an electromagnetic field. Read all about it:

https://en.m.wikipedia.org/wiki/Electromagnetic_field

>>>>D-

And people say I enjoy shooting fish in a barrel. 
Audio signal is electrical waves that represents sound waves in analog in digital it's binary.
I liked millercarbon’s answer.
Bravo Millercarbon!
Too many of us , myself included, are afraid to recognize the miraculous in the mundane or sometimes maybe just too preoccupied with the trivial.
Thank you Millercarbon for providing a visualization connecting atoms and physics for this history major!
Post removed 
I'm not touching that, "It looks infected":.....
Audio signals are mundane there's no miracles involved. No E=mc^2 we aren't splitting atoms. Audio signals aren't sound they are representations of sound in the form of electrical waves propagated through a conductive material in most cases copper. If you want a visualization for a history major on physics try Brian Greene "The Elegant Universe ".  Let's return to the mundane question of audio signals and leave the miracles for religious charlatans there's enough charlatans in audio as it is. 
Well i'll be ! 
 And all this time I was a'thinkin they were made from "Little girls dreams, Rainbows and Unicorn farts..........."
a re-creation of an acoustic wave(s) involving continuously varying amplitude(s) and frequency(ies).

captured via _____, recreated via _______
  djones51 ...
   
  • "Let's return to the mundane question of audio signals and leave the miracles for religious charlatans ..."

"That which is hidden from the most learned is revealed to mere children."
When I was a child, I talked like a child, I thought like a child, I reasoned like a child. When I became a man, I put the ways of childhood behind me.
The sum of their educational growth = an Online Degree, from Wiki  (iow: a BS Degree).
Knowledge can be defined as what’s left after you subtract out all the stuff you learned in school but forgot a long time ago. Past a certain point information retention is replaced by a different kind of retention. 😬
That’s literally the meaning of E=mc2. Energy, a force, equals mass, a thing. Times the speed of light squared. So you can say its a force or a charge, or you can say its a thing or a medium. It all depends on your point of view.

The thing I like most about Miller is how he teaches us to be worse versions of ourselves. As he’s said to my posts I now return the favor:

Miller’s interpretation of the Einstein’s energy-mass equivalence formula is utter rubbish.


Unlike Miller I’ll point you to sources to prove my point of view. Please read the section "Meaning of the strict formula" in the wikipedia article here: https://en.wikipedia.org/wiki/Mass%E2%80%93energy_equivalence

Best,
E
Be happy with what you got. I’m pretty sure they don’t teach physics courses in the 4-H Club. 🍀 🐄

Thanks to Millercarbon for his very lucid account of the physics of audio transmission. I’d add a brief philosophical remark. The talk of “forces,” “fields,” and so on in physics is very useful for calculating and predicting outcomes, but it does not even raise the question of what “forces” and “fields,” etc., actually are. As Niels Bohr wrote, “It is wrong to think that the task of physics is to find out how nature is.  Physics concerns what we can say about nature.” That is, physics stops at the observable phenomena, which are external to our own minds, and “knowable” only by virtue of our minds and bodies. If we were different kinds of animals (mantis shrimp, for instance, which have 17 color receptors as compared to our 3, or bats that “hear” what we see, or dogs that smell what we have no access to at all), we would “know” a very different world. To say “force moves…” is pretty much the same thing as to say that sleeping pills induce sleep because of their somnolent properties. We can describe these properties with remarkable precision, thanks in part to the importation of mathematics into physics in the early modern period (Newton, Descartes, et at.). But our descriptions merely presuppose the observable phenomena and the structures of mind that make observation of them possible. The forces themselves remain occult qualities. If our physical and mathematical descriptions were equal to the phenomena they describe, then the real meaning of existence could ultimately be expressed in a formula—as Douglas Adams parodies this point, the meaning of life might be “42”! 

So: what are the phenomena Millercarbon so succinctly describes? 

Ah, there’s the rub! There are many “answers,” but none of them are definitive. And this fact is itself instructive. The “reality” we presume to “understand” in physics is, in itself, necessarily beyond our grasp. To take Shakespeare out of context, there is more in heaven and earth, Horatio, than is dreamed of in your philosophy—or science. 

And so, there remains room for speculation, mystery, and the many emotive features we, as audiophiles, are so thrilled by that we’re willing to part with large sums of money to achieve it. 


sniff

The forces themselves remain occult qualities. If our physical and mathematical descriptions were equal to the phenomena they describe, then the real meaning of existence could ultimately be expressed in a formula—as Douglas Adams parodies this point, the meaning of life might be “42”!

So: what are the phenomena Millercarbon so succinctly describes?

Ah, there’s the rub! There are many “answers,” but none of them are definitive. And this fact is itself instructive. The “reality” we presume to “understand” in physics is, in itself, necessarily beyond our grasp. To take Shakespeare out of context, there is more in heaven and earth, Horatio, than is dreamed of in your philosophy—or science.

And so, there remains room for speculation, mystery, and the many emotive features we, as audiophiles, are so thrilled by that we’re willing to part with large sums of money to achieve it.


>>>>>English major, right?
djones51

"When I was a child, I talked like a child, I thought like a child, I reasoned like a child. When I became a man, I put the ways of childhood behind me."

And as we all did, you had the innocence of a child, the open heart of a child, the joy of a child, and the faith of a child. Such a shame that with our passing into manhood, we've put all of that behind us.

Frank


Three quarks for Muster Mark!

I don't recall who said it, but to paraphrase, the most amazing fact about the universe is that we can comprehend it and our place therein.  The universe we observe has rules that can be described by human invented mathematics.  Working scientist don't give much thought to "what is mass".  It's a word that describes phenomena that they can predict and measure.  Only philosophy majors, usually after a few drinks, give a thought about what it is.
Mass. Of course the audio signal in cables and wires has no mass if you subscribe to the idea that it’s an electromagnetic wave. You know, with the mass of photons these days being what it is. Jump on it!
*S* So, in 25 hours and 18 minutes...

Alan Watts to quantum cosmology, with a brief stint of M.C. Hammer.

(At least the word 'audio' showed up...occasionally....) ;)
Toss in some Babble verses and it's a show that never ends.
Oh, you mean like this? 😃

djones51
When I was a child, I talked like a child, I thought like a child, I reasoned like a child. When I became a man, I put the ways of childhood behind me.
Getting back to the dodgy subject of does the signal travel inside the conductor or outside the conductor, the speed of the signal in a copper conductor is measured to be some high fraction of the velocity of light in a vacuum, let’s say it’s 85% of c for the sake of argument. But if the signal were mostly traveling OUTSIDE the conductor - in air - as some have argued, wouldn’t the speed of the signal be a lot closer to the speed of light in a vacuum? Or about 99.9% of c, not 85%.
That was in response to this 


"
That which is hidden from the most learned is revealed to mere children."

I doubt anyone has a stereo system in a vacuum. Anyway speaker wire doesn’t carry audio signals but an electrical description of the audio. That electrical pulse is carried in the wire mostly the outer 1/3 of the wire.
djones51
...  speaker wire doesn’t carry audio signals but an electrical description of the audio ...
No, it's an audio signal, an analog of the sound.
That electrical pulse is carried in the wire mostly the outer 1/3 of the wire.
It's not a pulse at all. It's continuous, an analog.
No it's an electrical description of the audio signal of the analog sound. Making the electricity vary between positive and negative at the speed and amplitude of the sound makes the speaker reproduce the sound. It's continuous but not in a linear way more like a varying pulse. Just like digital is a description of the audio signal in binary sent in packets the sum of which is a stream to a DAC or speaker if it's an active speaker. 
djones51
Making the electricity vary between positive and negative at the speed and amplitude of the sound makes the speaker reproduce the sound.
Yes, but that is not what an amplifier does; the audio signal is already varying from positive to negative before it reaches the amplifier. We know that because audio signals are AC. The amplifier simply provides more power for the analog audio signal.

The very definition of analog is what seems to be what’s confusing you:

"being a mechanism or device in which information is represented by continuously variable physical quantities ... something that is similar or comparable to something else either in general or in some specific detail : something that is analogous to something else."

I’m not sure why you now believe the obviously analog signal is some kind of magical "electrical pulse." You seemed to understand this earlier when you wrote:
Audio signal is electrical waves that represents sound waves in analog
I’m sure you can understand that a wave is not a pulse!
I never said the amplifier created the audio signal. OK wave not pulse, pulse would be digital. The point I was making is an " audio signal" in wire is an electrical description of that signal and it travels in the wire mostly the outer third though all of the wire carries it especially if the speaker wire is no more than 1/2 inch thick. 
, and what exactly is the medium it travels through in a cable?? thecarpathian

Note where the overwhelmingly majority of the signal travels. Click on the Link below the quoted material and look at the diagram provided.

Coaxial cable Poynting vector in a coaxial cable, shown in red.

For example, the Poynting vector within the dielectric insulator of a coaxial cable is nearly parallel to the wire axis (assuming no fields outside the cable and a wavelength longer than the diameter of the cable, including DC). Electrical energy delivered to the load is flowing entirely through the dielectric between the conductors. Very little energy flows in the conductors themselves, since the electric field strength is nearly zero. The energy flowing in the conductors flows radially into the conductors and accounts for energy lost to resistive heating of the conductor. No energy flows outside the cable, either, since there the magnetic fields of inner and outer conductors cancel to zero.

Resistive dissipation

Electrical energy delivered to the load is flowing entirely through the dielectric between the conductors.

Very little energy flows in the conductors themselves,

https://en.wikipedia.org/wiki/Poynting_vector#Coaxial_cable

https://en.wikipedia.org/wiki/Poynting_vector

.

The signal is not the Poynting vectors. The direction of the Poynting vectors are not even in the direction of the current. You know what a vector is, right? We’ve already covered all that. Come on, guys. Wake up and smell the coffee! ☕️ Stop trying to cherry pick 🍒 Wikipedia. Photons have no problem traveling through solid material like say, glass and water. That’s pretty obvious. Especially for high energy photons.
Electrical energy delivered to the load is flowing entirely through the dielectric between the conductors.

Very little energy flows in the conductors themselves,

Stay on point.....
It’s you who can’t keep it straight. The signal is not the Poynting vectors. 
I don't think anyone uses transmission lines for interconnects or speaker cables. 
Oh, brother! 😧 Well, something’s being transmitted!
Well that's where Poynting vectors come in, transmission lines. 
Huh? Then maybe you can tell me if this is where all those guys get their info. 
An excerpt from Wikipedia,

Coaxial cable[edit]Poynting vector in a coaxial cable, shown in red.

For example, the Poynting vector within the dielectricinsulator of a coaxial cableis nearly parallel to the wire axis (assuming no fields outside the cable and a wavelength longer than the diameter of the cable, including DC). Electrical energy delivered to the load is flowing entirely through the dielectric between the conductors. Very little energy flows in the conductors themselves, since the electric field strength is nearly zero. The energy flowing in the conductors flows radially into the conductors and accounts for energy lost to resistive heating of the conductor. No energy flows outside the cable, either, since there the magnetic fields of inner and outer conductors cancel to zero.

Mass? I haven't been to mass in decades.
Uh yeah OK, you've lost me.  coaxial cables are transmission lines. I don't  think to many people use them RG6 or RG59 as speaker cables or interconnects I suppose they could. 
Poynting vectors apply to any conductor where there is an EM wave, as in any cable or power cord. No? I don’t particularly care about Poynting vectors as I don’t think they completely explain the audio signal in wire or “directionality“ or how the audio signal is affected by vibration, among other debatable audiophile topics. I suspect Poynting vectors are more useful to skeptics.
OK, you're beyond me. It has to do with flow of energy in EM field or something but I don't see how it has anything to do with the question of what's an audio signal and what's it travel through.