There is no shouting.
What it is indicating is that the 7th angel will blow his trumpet for 15-30 seconds , or less, and then announces with his voice the time has come for God to judge the earth and put an end to Satan's and his angels' rule.
None of the events of the seals have begun yet. The seal events are a different issue than the 7 angels having the trumpets.
There is no angel recorded in the 6th seal event in Revelation 6:12-17.
Revelation 11:15
"And the seventh angel sounded; and there were great voices in heaven, saying, The kingdoms of this world are become the kingdoms of our Lord, and of his Christ; and he shall reign for ever and ever."
It was not the angel speaking. It was all the voices in heaven speaking. The angel kept on sounding the Trumpet.
As for the Seals being opened, yes, they have started. Obviously not many would notice. Most will only look back in hindsight. Do you remember this happening? Revelation 5:12-14
12 Saying with a loud voice, Worthy is the Lamb that was slain to receive power, and riches, and wisdom, and strength, and honour, and glory, and blessing.
13 And every creature which is in heaven, and on the earth, and under the earth, and such as are in the sea, and all that are in them, heard I saying, Blessing, and honour, and glory, and power, be unto him that sitteth upon the throne, and unto the Lamb for ever and ever.
14 And the four beasts said, Amen. And the four and twenty elders fell down and worshipped him that liveth for ever and ever.
If every creature stopped what they were doing, even sleeping, and said, "Blessing, and honour, and glory, and power, be unto him that sitteth upon the throne, and unto the Lamb for ever and ever.", would they have thought about it one second after the fact? Or would they have shrugged, and thought, what was that, for a second and went back to their usual business?
If it happened in the next 10 years, would it be a planned event by a one world government? Would it be coordinated with the rest of Creation? Something like that would only come from God, and the vast majority of people on earth would not even know what happened.
Yes there are angels in the 6th Seal event. Remember John is using symbolic terms:
"And the stars of heaven fell unto the earth, even as a fig tree casteth her untimely figs, when she is shaken of a mighty wind."
Jesus said in Matthew 24:31
"And he shall send his angels with a great sound of a trumpet, and they shall gather together his elect from the four winds, from one end of heaven to the other."
Jesus literally claims the angels are coming with the trump of God. John declares the angels coming as the stars coming down easy like fig leaves. Sounds like all the stars (angels) are coming to earth.
The angels came at the first coming to Bethlehem. This time they will come to every place on earth there are humans living. Even Antarctica if there are humans camped out there.