Charple is the first enemy you encounter in the four-part map series. He first appears in the vents of foundonthetape_2.bsp, and is always around, lurking.
When you know Charple is coming, the screen will begin to shake with tasteofblood.ogg getting louder. Smoke accompanies Charple, and when you get too close, he'll appear and crash Half-Life 2. However, in GMod he just flies past the player, facing backwards. Charple can go through walls, but is in a set path, similar to Armless, except he loops his track. When Carple is not chasing you, Onthehunt.ogg plays.
It is possible that Charple could be making the noises that you hear In foundonthetape_2.bsp