Megaphone (noun)

A device that amplifies the sound of a person's voice and projects it forward, typically in the shape of a cone or horn and operated by a hand-held microphone.

Origin:

Late 19th century: from mega- + -phone.

Examples:

1. The coach used a megaphone to give instructions to the team.
2. The protester used a megaphone to amplify his voice.
3. The megaphone is a powerful tool for amplifying sound.
4. The megaphone is a common tool for public speaking.
5. The megaphone is a useful tool for making announcements at a large event.