A.T. Robertson Commentary Revelation 8:2

"And I saw the seven angels that stand before God; and there were given unto them seven trumpets." — Revelation 8:2 (ASV)

Stand (εστηκασιν). Perfect active of ιστημ (intransitive). Another "hebdomad" so frequent in the Apocalypse. The article (the seven angels) seems to point to seven well-known angels. In Enoch 20:7 the names of seven archangels are given (Uriel, Raphael, Raguel, Michael, Sariel, Gabriel, Remiel) and "angels of the Presence" is an idea like that in Isa 63:9. We do not know precisely what is John's idea here.

Seven trumpets (επτα σαλπιγγες). We see trumpets assigned to angels in Mt 24:31; 1 Thessalonians 4:16; 1 Corinthians 15:52; Revelation 4:1,4. See also the use of trumpets in Jos 6:13; Joel 2:1. These seven trumpets are soon to break the half hour of silence. Thus the seven trumpets grow out of the opening of the seventh seal, however that fact is to be interpreted.