Objection 1. It would seem that the sound of the trumpet will not be the cause of our resurrection. For the Damascene says (De Fide Orth. iv): "Thou must believe that the resurrection will take place by God's will, power, and nod." Therefore since these are a sufficient cause of our resurrection, we ought not to assign the sound of the trumpet as a cause thereof.
Objection 2. Further, it is useless to make sounds to one who cannot hear. But the dead will not have hearing. Therefore it is unfitting to make a sound to arouse them.
Objection 3. Further, if any sound is the cause of the resurrection, this will only be by a power given by God to the sound: wherefore a gloss on Psalm 67:34, "He will give to His voice the voice of power," says: "to arouse our bodies." Now from the moment that a power is given to a thing, though it be given miraculously, the act that ensues is natural, as instanced in the man born blind who, after being restored to sight, saw naturally. Therefore if a sound be the cause of resurrection, the resurrection would be natural: which is false.
On the contrary, It is written (1 Thessalonians 4:15): "The Lord Himself will come down from heaven... with the trumpet of God; and the dead who are in Christ shall rise."
Further, it is written (John 5:28) that they "who are in the graves shall hear the voice of the Son of God... and (John 5:25) they that hear shall live." Now this voice is called the trumpet, as stated in the text (Sent. iv, D, 43). Therefore, etc.
I answer that, Cause and effect must needs in some way be united together, since mover and moved, maker and made, are simultaneous (Phys. vii, 2). Now Christ rising again is the univocal cause of our resurrection: wherefore at the resurrection of bodies, it behooves Christ to work the resurrection at the giving of some common bodily sign. According to some this sign will be literally Christ's voice commanding the resurrection, even as He commanded the sea and the storm ceased (Matthew 8:26). Others say that this sign will be nothing else than the manifest appearance of the Son of God in the world, according to the words of Matthew 24:27: "As lightning cometh out of the east, and appeareth even into the west, so shall also the coming of the Son of man be." These rely on the authority of Gregory [Moral. xxxi, as quoted by St. Albert the Great, Sentent. iv, D, 42, 4] who says that "the sound of the trumpet is nothing else but the Son appearing to the world as judge." According to this, the visible presence of the Son of God is called His voice, because as soon as He appears all nature will obey His command in restoring human bodies: hence He is described as coming "with commandment" (1 Thessalonians 4:15). In this way His appearing, in so far as it has the force of a command, is called His voice: which voice, whatever it be, is sometimes called a cry [Matthew 25:6, as of a crier summoning to judgment; sometimes the sound of a trumpet [1 Corinthians 15:52; 1 Thessalonians 4:15, either on account of its distinctness, as stated in the text (Sent. iv, D, 43), or as being in keeping with the use of the trumpet in the Old Testament: for by the trumpet they were summoned to the council, stirred to the battle, and called to the feast; and those who rise again will be summoned to the council of judgment, to the battle in which "the world shall fight... against the unwise" (Wisdom 5:21), and to the feast of everlasting solemnity.
Reply to Objection 1. In those words the Damascene touches on three things respecting the material cause of the resurrection: to wit, the Divine will which commands, the power which executes, and the ease of execution, when he adds "bidding," in resemblance to our own affairs: since it is very easy for us to do what is done at once at our word. But the ease is much more evident, if before we say a word, our servants execute our will at once at the first sign of our will, which sign is called a nod: and this nod is a kind of cause of that execution, in so far as others are led thereby to accomplish our will. And the Divine nod, at which the resurrection will take place, is nothing but the sign given by God, which all nature will obey by concurring in the resurrection of the dead. This sign is the same as the sound of the trumpet, as explained above.
Reply to Objection 2. As the forms of the Sacrament have the power to sanctify, not through being heard, but through being spoken: so this sound, whatever it be, will have an instrumental efficacy of resuscitation, not through being perceived, but through being uttered. Even so a sound by the pulsation of the air arouses the sleeper, by loosing the organ of perception, and not because it is known: since judgment about the sound that reaches the ears is subsequent to the awakening and is not its cause.
Reply to Objection 3. This argument would avail, if the power given to that sound were a complete being in nature: because then that which would proceed therefrom would have for principle a power already rendered natural. But this power is not of that kind but such as we have ascribed above to the forms of the Sacraments (Sent. iv, D, 1; I, 62, 1,4).
Source: Summa Theologica (New Advent)