loud hailer
/ˈlaʊdˌheɪlər/
noun
- A portable electronic device that makes a person's voice louder, used to address a crowd or communicate over a distance.
- The ship's captain picked up the loud-hailer to give orders to the crew on deck.
- At the protest, the organizer spoke through a loud-hailer so everyone could hear.
- The lifeguard used a loud-hailer to warn swimmers about the strong current.