Because it is distributed over three passages (Rev 10:5-7; 11:14-19 and Rev 14:6-20), the effect of the seventh trumpet is not readily apparent.

When the seventh trumpet sounds (Rev 11:15):

Heavenly beings shout out great praise and worship.

They proclaim that the kingdom of the world, previously ruled by Satan, has become the kingdom of God and His Son Jesus (Rev 11:15-17).

They announce the coming time of judgment of the dead and of rewards for the bond servants, prophets and the saints (Rev 11:18).

The heavenly temple of God opens and reveals the ark of His covenant.

The open temple allows the seven angels with the seven plagues to come out (Rev 15:5-6). Once out, one of the four living creatures gives each a golden bowl of God's wrath. These plagues are the last of God's plagues, and once dispensed with a bowl of God's wrath, the wrath of God is finished (Rev 15:1).

Three angels flying in midheaven make three pronouncements.

The first angel preaches to the whole world the gospel in a manner that all would understand and have no excuse (Rev 14:6-7; Matt 24:9-14; Mark 13:9-10).

The second angel, following the first, proclaims the fall of the secular worldview that denies the existence of God and sin; the lifestyle that is motivated by pride and power and attracts all cultures and people, intoxicating and pleasurable, will be judged for its immorality (Rev 14:8).

The third angel, following the previous two in speaking to all human beings of the world, condemns all those who have the mark of the beast (Rev 14:9-11).

The final result of the seventh trumpet is the appearance of the reapers, and the reaping that occurs is in the figurative sense and reminiscent of the Parable of the Tares.

Jesus Christ, makes His Second Coming, sitting on the cloud wearing a golden crown, wields a sharp sickle (Rev 14:1-16).

An angel, who came out of the heavenly temple, wields a sharp sickle (Rev 14:18-19).

And while the seventh trumpet heralds the third and final woe, it has yet to be revealed…

For deeper study:

The Seventh Trumpet

The Parable of the Tares