Don't mind him, that's just Charles, he's a bit loopy sometimes, but he does write nice poetry.
I didn't think HAARP was still operational? It was supposed to be dismantled this year?
It was an attempt to improve communications by using high power radio to ionize part of the upper atmosphere to bounce UHF signals off.
That sort of ionospheric propagation occurs naturally when there is strong solar activity, and sometimes meteor showers. A lot of amateur radio distance records have been set using meteor scatter.
So, it's not an acoustic signal being transmitted, there would need to be some secondary mechanism for sound to be generated.
No idea what the sounds are, another mystery.