Easton's Bible Dictionary: M. G. Easton, M.A., D.D.
Were of a great variety of forms, and were made of divers materials. Some were made of silver (Num. 10:2), and were used only by the priests in announcing the approach of festivals and in giving signals of war. Some were also made of rams' horns (Josh. 6:8). They were blown at special festivals, and to herald the arrival of special seasons (Lev. 23:24, 25:9; 1 Chr. 15:24; 2 Chr. 29:27; Ps. 81:3, 98:6).
"Trumpets" are among the symbols used in the Book of Revelation (Rev. 1:10, 8:2).