They range from player to player, the most common being screams, someone crying, and a Chainsaw revving up. Many players believe they are made by some ghosts of Pedestrians who killed themselves at the cabin, with constant reports of players seeing a hung body in the cabin and a pedestrian running off the edge with the sounds. In the mission Badlands, CJ kills an ex-police officer and takes a picture of his corpse. The ghost reported in the cabin could be a manifestation of the dead police officer. Many players have seen a correlation between the screams and Bigfoot or the Yeti, but there is very little evidence to support these claims. In real life, it is believed that Sasquatches (the cryptid both Bigfoot and the Yeti are based upon,) use yelling and banging on sticks to contact other members and search for mates.
This myth can also be a coincidence from the Falling Pedestrian on Mount Chiliad as the pedestrians often scream as they fall, possibly causing the "scream" factor.