Trumpets feature widely in the Bible. In the Old Testament the sounding of trumpets regulated the religious and practical life of Israel, and they were also used in warfare for commanding the armies.
Early trumpets were made of ram's horns (see Joshua 6:4), and these were always used for some religious purposes, but trumpets were also made from beaten silver. They were used to call the people together for special assemblies, and they announced the feast days and the New Moons. In battle, the trumpet call was sometimes addressed to God, who had promised that when He heard the sound of the trumpet, He would deliver His People from their enemies (see Numbers ch.10). In times of national or local danger, the trumpet would sound the alarm (see Zephaniah 1:16). God Himself will sound the trumpet which will announce to the world that Christ has returned as King to Zion (see Zechariah 9:14).

The apostle John in the Book of Revelation describes in figurative language how a series of trumpet calls will herald the events which will lead up to the time when "the mystery of God will be accomplished" (Revelation 10:7), and "the last trumpet" (1 Corinthians 15:52) will call the dead from their graves at the resurrection, and call God's elect together (see Matthew 24:31).

Paul tells us to preach God's word clearly and intelligently, because:

"If the trumpet does not sound a clear call, who will get ready for battle?" (1 Corinthians 14:8).