This might be a silly little mechanic, but I noticed in the latest trailer for the game Machine Hunt, every single COG machine type you face has a warning horn or siren to announce its presence, from the spiders, to the tanks and even the structures. I was thinking why not your giant drill having a horn of its own for when it’s on the move and can be pressed at any time. The enemy drills can even have their own horns. The sounds they make are similar to a real world concept called the “drill horn” but in lower pitch as the drill you operate is huge. You do extend your drill like a train anyways.