The broadcast is a recording of the emergency broadcast system that most governments with TV infrastructures employ. It's saying "THIS IS NOT A TEST". Presumably, it's talking about a broadcast that happened just before Talos landed, but it's unclear what the rest of the recording is saying or why something like that would be playing on endless loop in Theta. Here's the audio in question:
I think I pick out snippets of them saying "Air Force", "July 3rd", "earthquake", and "killed him and filled his place". There's a lot more than that, though, and I have no idea what it could be referring to. The only thing in the SOMA timeline I can find regarding July 3rd is that's the date that Catherine gets approval to start scanning people for the ARK.
And I don't hear anything in the recording explaining why it's placed against the distorted footage of a satellite/some solar panels/whatever on (presumably) the moon.