That's basically all you'll hear is an open carrier noise.
This is a very specialized communications network that is aboard the 4 E-4B 747-200 NAOC & a few other aircraft in the US. Like AF-1 VC-25A's (747-200). The E-6's can do BURN CH also.
It's also called Northstar / Orderwire, C3, GEP (Ground Entry Point) WBFM. Wright Patterson AFB is the closest GEP station around here. This system keeps an open communications line between Commanders of nuclear forces during or after a Nuke attack.
It's supposed to Burn a signal thru all the noise of an attack. Hence the term BURN CH (Channel). The system is also Hardened against EMP (Electro Magnetic Pulse) effects from the blast. Basically it sounds like an open mike, that you can sometimes hear voice traffic, & a phone ringing in the background, that nobody answers.
I believe there is 8 channels above the main freq, & 8 channels below. That's why it's hard to hear any talking, they're slightly off freq.
I hope the link below works.
Some info on the E-4B 747's.
Federation of American Scientists :: E-4B National Airborne Operations Center
Good job everyone on posting today.