When a system absorbs energy most efficiently because it's being driven at just the right frequency, like pushing a swing at the moment it naturally swings back. In PEMF, some researchers believe that specific pulse frequencies may resonate with cellular processes, though the science is still evolving. Resonance occurs when the driving frequency matches the system's natural oscillation frequency.
A real field pulse over time. The height of the pulse is its amplitude, how strong the field gets, separate from how often the pulse repeats. After the pulse the coil rings, a fast shrinking oscillation at the coil's natural frequency; the time from one ring peak to the next is one cycle of that ring frequency. A coil driven at its natural frequency takes up energy most efficiently, which is resonance.
