A bug is affecting some players in PlayerUnknown's Battlegrounds right now, causing them to hear discussion from people other than their teammates.
The official Twitter account for the game has acknowledged the problem, which means that any of the other million concurrent players could pop up in your ear, and has stated that it is currently being worked on.
We are aware of the issue with voice chat. You may hear voices of players that are not in your team. We will fix this issue soon.
— PLAY BATTLEGROUNDS (@PUBATTLEGROUNDS) September 14, 2017
You can Ctrl + T to turn voice off, of course, which you'll want to do, because the biggest danger you face out there, on PUBG's damned island, is the possibility of humanising the players on other teams. You don't want to grow attached to your prey, with friendship developing, or worse.
Can love bloom on the battleground? Better not to find out.
In any case, the problem is likely to be fixed soon.