wlutke
geoffkait
"Acoustic waves are on a different spectrum."
That’s the root of my question. Below radio frequencies is the ultrasonic, sonic and subsonic, none of which can be broadcast without an electromagnetic carrier frequency. Does that not preclude a subsonic electromagnetic wave?
>>>>>The “electromagnetic spectrum” goes from DC 0 Hz to visible light and beyond, with increasingly more energetic photons as the particle involved. That’s why I used the ELF as an example of extremely low frequency EM radiation/wave. ELF is a radio program/transmitter, thus the ELF Signal is a radio frequency. I realize we usually think of “radio frequencies” as very high frequencies, like microwave.
The Schumann frequency - both the natural one and the one generated by all these various devices - except the CD - is an electromagnetic radiation/wave. And obeys the laws of such waves, I.e., Maxwell equations, speed of light in a vacuum, etc. The CD generates an acoustic wave of frequency 7.83 Hz.