105 But it is now time, I think, to speak of the trumpets since my discourse is nearing its end, that the trumpet may also be the sign of the finishing of my address. We read of seven trumpets in the Revelation of John, which seven angels received. And there you read that when the seventh angel sounded his trumpet, there was a great voice from heaven, saying: “The kingdom of this world has become the kingdom of our God and of His Christ, and He shall reign for ever and ever.” The word trumpet is also used for a voice, as you read: “Behold a door opened in heaven, and the first voice which I heard, as of a trumpet speaking with me and saying, Come up hither, and I will show you the things which must come to pass.” We read also: “Blow up the trumpet at the beginning of the month [the new moon]”; and again elsewhere: “Praise Him with the sound of the trumpet.”
Source: On the Death of Satyrus (New Advent)