There seems to be some confusion going on here. If I'm wrong in my assessment, I apologise.
Several times I thought MrSkinny was going to straighten things out, but he might have been too tired.
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Radio emissions are an electromagnetic phenomenon traveling at the speed of light in the particular medium; also can be thought of as photons, but not usually at the frequencies dealt with in this thread.
Sound waves are physical displacement waves of a carrying medium (solid or fluid) usually as compression fronts, but can be lateral. They travel at the speed of sound in that medium.
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Transducers (speakers) and antennae only radiate frequencies they are supplied with by a driving signal. (OK, if nonlinearities come into play, harmonics or subharmonics are there, but at fractional power.) The frequency capabilities depend on the physical size of the radiator: higher frequencies require smaller radiators.
Transmission lines (even rudimentary ones like speaker leads and power lines) carry electrical signals of current and voltage that may or may not vary with time, and if varying, can possess frequencies from zero to almost the infrared frequencies. The signal on the line depends on the driving source (power amp) mostly. Low quality lines lose more high frequency power than better ones, and all have an upper limit on what they will carry with useful output.
Signals on a line don't care if they are meant to be sound or radio, they are just voltage and current. What is at the load end determines what form the "radiation" will take.
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Here I use transducer to be a device taking a varying voltage or current input and converting that to a mechanical replica of the variations of the input.
An antenna converts the electrical input to a pair of perpendicular electric and magnetic fields bound together and propagating away through space at the speed of light.
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What we call sound is usually (for humans) considered to be from 20 Hz to 20 KHz, a three decade range.
Radio is considered by most laymen to be from 30 KHz to possibly 300 GHz, a seven decade range.
The reality is that, being entirely different forms of radiated energy, the radio (EM) spectrum extends far BELOW what we can hear, and sonics extend far into the upper frequencies of what we commonly think of as the RF bands: Both forms CAN cover the same ranges of frequencies.
The military uses transmitters in the low end of our range of hearing, but we never hear it because it is EM and not sound.
There are many uses of sonic energy far into the same band used by radio and television, but your all-band receiver wont hear it, because it is mechanical vibration and not EM.
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Sound in air at normal conditions won't carry well at these higher frequencies, but they carry well in liquids and solids
Radio at the lowest frequencies can communicate globally with submarines or underground recievers.
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I tried to keep this non-technical, but to still convey the needed information.
I hope I succeeded.
Dave
ETA: It appears that in the time it took me to read all the posts up to that time and then compose my reply (several hours due to an unending stream of interruptions) that {Mr NoToobs (forgot the name)} skidded into what I wanted to clarify. Oh well, maybe someone will get something out of my post.
