It depends on how you propagate it whether it is audio or RF.
If you are transmitting audio you are transmitting an acoustic wave.
If you are transmitting RF then you are transmitting an
electromagnetic wave.


Thank you, this makes sense.
I was trained in radio and perhaps was being too simplistic. Yes, I was not
differentiating between acoustic pressure waves and EM waves. I should study
the workings of the transducer. Can anyone help here?
Does a transducer have a diaphragm vibrating at 200K?

I must confess that my training started over 50 years ago (in the RAF). It
was much simpler then (fishfinder, what's that?), and I now feel rather left
behind.

Henry