The jury’s out on what’s causing the sound (which is far, far below the level of human hearing) and a whole lot of theories are being tossed around about it. Everything from magnetic fields to ionization of particles shearing themselves from the traveling comet is suspect at this point.
“This is exciting because it is completely new to us. We did not expect this and we are still working to understand the physics of what is happening.” – RPC principal investigator Karl-Heinz Glaßmeier
Until there’s an answer, which probably won’t be soon because space is just weird, we’re going to assume that the comet is either harboring a Predator who’s looking for payback, the mobile rehearsal space for a marimba-playing Cantina Band member or that we’ve discovered the dial-up connection for an alien race.