In an Event Tick, you can use Line Trace By Channel to trace down (negative Z direction) from the center of your Pawn to the underlying terrain. By breaking Hit Results, you will see there is a Phys Mat property. From that one you get Surface Type and then Switch among the different types of physical surfaces to make different sounds. It doesn’t matter that the Pawn doesn’t have a physical body because you use raycasting to “sample” the underlying material and get its physical surface type.