If its a high frequency wave, then you would "hear" it with the skin and other tissue on your head rather than your actual ears. Earplugs wouldnt really help.

How it works: you can hear a high frequency wave if its modulated at audible frequency. If it's switched on and off at a relatively low frequency, you can sense the presence and absence of the high-frequency vibrations. Those waves are poorly absorbed from the air, but once they make it into the body they are transmitted much more easily by tissues besides bone. So your ears are not much better than the rest of your skin, which acts like a funnel for sound, diverting it to your cochlea.

Did you hear the recording? That's entirely the range of sounds that good hearing protection dampens.

There's an actual recording of signals inducted in wires - either from soundwaves moving a magnet in a field (sound picked up by a mic), or inducted by in the wires by electromagnetic radiation, surely?

I agree it might be unlikely that one signal might induce sound in a human that sounds like the sound a recorder might record - but I don't know. I just know that it's trivial for radiation to fool sound equipment (eg: cell phone signal too close to a speaker/mic/amplifier).

However, if this is a sophisticated weapon, there might be two signals: high power that target humans, lower power that target recording equipment?