When the priest calls down the Holy Spirit he says the following:
P: And make this the Body of Thy Christ.
The people then respond:
P: And make this the Blood of Thy Christ.
P: Changing them by Thy Holy Spirit.
Pe: Amen. Amen. Amen.
This is the way it is done in Antiochian and Greek parishes. But it is patently incorrect. The "Amens" are the prerogative of the Deacon only. If there is no deacon, the "Amens" are again reserved to the priest. However, because of the continued absence of deacons and also because of the influx of converts from Protestant backgrounds where there is no distinction between clergy and laity, the people have taken the deacon's role for themselves. The people should be singing the hymn "We hymn Thee, We bless Thee" but this hymn has even been moved to be sung AFTER the epiclesis. It makes no sense to place it there since we should be hymning and blessing the Lord because He is transforming the bread and wine into the Body and Blood of Christ by the power of the Holy Spirit.
Fr. Alexander Lebedeff has this to say about such liturgical innovation:
Similarly, the proclaiming aloud of three "amens" after the epiclesis is another uncalled-for expression of fervor, meaning it is not specified in the rubrics of the service. The service books state clearly that the three "Amens" are said by the Deacon. It does not say: "and the people say—amen, amen, amen."
Again, this is an example of laypeople usurping the prerogative of the Deacon, who participates actively in the consecration of the Holy Gifts, and gives both the invitations ("Bless, Master, the Holy Bread." etc.) and the responses, including the "Amens." It would be inappropriate for the altar servers to participate in these responses, even though they are right there and can see and hear what is occurring. During the epiclesis, the choir is singing the solemn hymn "We sing unto Thee...", the Royal Doors are closed, and the faithful stand in silent prayer that should not be interrupted by any amens, however well-intentioned. In order to even know when the exact moment to say these amens occurs, the congregation would have to hear the words that the Priest is supposed to pronounce quietly during the singing of the hymn. Either the Priest would have to say them quite loudly, drowning out the singing, or the singing would have to stop so that you could hear what the Priest was saying. Both would be a violation of the order of the service (as is any reading aloud by a Priest of any prayer meant to be read quietly or silently).
Actually, there are a variety of dynamics indicated in the services for prayers. Some are said quietly (in a low voice), some are said loudly (in a great voice), some are said silently (no voice). We should humbly defer to the holy authors of these services and follow their directions. Whenever we want to introduce something "of our own," we not only violate the service rubrics, but we violate the unity of the church.
All such "unique" practices should be patiently and lovingly eliminated.
The entire article can be referenced here.
Such practices need to stop. I'm no ordained Deacon and thus I should not say Amen. Neither are the people in the nave. This work is only being done in the sanctuary, the result of which will then be carried out and distributed to the faithful. Then, we may say "Amen, amen, amen" to our hearts' content.