trumpet

Definition:

The term "trumpet" refers to an instrument for producing music or for calling people to gather together for an announcement or meeting.

A trumpet was commonly made from either metal, seashell, or an animal horn.
Trumpets were most commonly blown to call people to come together for battle, and for Israel's public assemblies.
The book of Revelation describes a scene in the end times in which angels blow their trumpets to signal the outpouring of the wrath of God on the earth.