Apocalypse Explained #530
530. Saying with a great voice, signifies manifestation. This is evident from the signification of "saying with a great voice," as being manifestation, here respecting the coming state of the church near its end, which is foretold in what follows. It is said "a great voice" because it has reference to the Lord and to the universal heaven (as has been said just above).
Revelation 18:16-17
16
And saying, Alas, Alas, that great city, that was clothed in fine linen, and purple, and scarlet, and decked with gold, and precious stones, and pearls!
17
For in one hour so great riches is come to nought. And every shipmaster, and all the company in ships, and sailors, and as many as trade by sea, stood afar off,