* Comparative: "The music got louder as the night went on."
* Superlative: "That was the loudest concert I've ever been to!"
* Command: "Can you speak louder please? I can't hear you."
* Describing a sound: "The thunder roared louder than ever before."
* Figurative language: "Her laughter grew louder with each passing day."
Remember that "louder" is used to compare the volume of a sound to something else, either explicitly or implicitly.