This is the first reference to trumpets in the Bible, and it is significant that the "voice" of the trumpet was coming not from man, but from God. The setting was the awesome scene at Mount Sinai, when the Lord gave Moses the Ten Commandments for His people.
The last reference in the Old Testament to trumpets again refers to God's trumpet. "And the LORD shall be seen over them, and his arrow shall go forth as the lightning: and the LORD God shall blow the trumpet, and shall go with whirlwinds of the south" (Zechariah 9:14).
The trumpet, as used in Israel (Hebrew shofar), was made of ram's horns and was used on many important occasions. One of the most notable was when the Israelites finally entered the Promised Land at Jericho. "So the people shouted when the priests blew with the trumpets: and . . . the wall fell down flat, . . . and they took the city" (Joshua 6:20). These were human trumpets, of course, but they were sounded with the authority of God and God gave the victory.
We also today can speak with the authority of God, if we speak His Word plainly and clearly. But "if the trumpet give an uncertain sound, who shall prepare himself to the battle?" (1 Corinthians 14:8).
We ourselves may soon hear the trumpet of God, for the return of Christ is drawing near. "For the Lord himself shall descend from heaven . . . with the trump of God" (1 Thessalonians 4:16). As we are caught up to meet the Lord in the air, we (like John long ago) will hear a voice "as it were of a trumpet," saying, "Come up hither" (Revelation 4:1), and then "shall we ever be with the Lord" (1 Thessalonians 4:17). HMM http://www.icr.org/article/5952/