The seven trumpets are sounded by seven angels and the events that follow are described in detail from Revelation Chapters 8 to 11.
According to Revelation 8:1-2 the angels were given these physical trumpets after the breaking of the seventh seal. These seals secure the document, that was in the right hand of Him who sits on the main throne (God the Father).
The trumpets are referred to in Koine Greek as salpingos, pronounced salpinx, a straight, narrow bronze tube with a mouthpiece of bone and a bell; they do not resemble modern trumpets.
The point of the trumpets are to warn the inhabitants of the World of the impending judgment that is to come. The trumpets are not symbolic, they are literal and heard by everyone on planet at the time. And not just the trumpets, there are a series of verbal warnings by the Angels that are also heard literally.
Revelation 14:6–10
6 And I saw another angel fly in the midst of heaven, having the everlasting gospel to preach unto them that dwell on the earth, and to every nation, and kindred, and tongue, and people,
7 Saying with a loud voice, Fear God, and give glory to him; for the hour of his judgment is come: and worship him that made heaven, and earth, and the sea, and the fountains of waters.
8 And there followed another angel, saying, Babylon is fallen, is fallen, that great city, because she made all nations drink of the wine of the wrath of her fornication.
9 And the third angel followed them, saying with a loud voice, If any man worship the beast and his image, and receive his mark in his forehead, or in his hand,
10 The same shall drink of the wine of the wrath of God, which is poured out without mixture into the cup of his indignation; and he shall be tormented with fire and brimstone in the presence of the holy angels, and in the presence of the Lamb: