Audio Log AST-AL-009 is located in the Overgrown Ruins (Biome 1), however the room is randomly generated. The room has an orb that drops red projectiles near the center with 4 broken platforms (view images for layout). The quickest way to generate it would be to start at Biome 1, go into the first two triangular blue doors you can find. If the room doesn't show up, go into the menu and Restart.