In Exodus 9:23, 29, this signifies truths divine which enlighten and perfect people in heaven, but terrify people in hell. (Arcana Coelestia 7573)

In Psalm 29:3, this signifies the Word in its power. (Doctrine Regarding Sacred Scripture 18[4])

When the Lord speaks through the heaven, it descends into the lower spheres and is heard as thunder. As He speaks through the whole of heaven at once, the sound is called 'seven thunders' in Revelation 10. 'Seven' signifies all, everything, and wholeness. This is why 'thunder' signifies instruction and perception of truth, and in this instance, the revealing and manifestation of truth. A voice from heaven is heard as thunder when it comes from the Lord, which can be seen in John 12:28-30, Job 37:4-5, 2 Samuel 22:14, Revelation 14:2, and Psalms 81:8. 'Great thunder,' as in Revelation 14:2, signifies the divine good of divine love.

(Odkazy: Apocalypse Explained 10, 14 [2]; Apocalypse Revealed 472; Revelation 2, 14)