Someone posted upthread the times when Jesus prayed aloud, and other scriptural references to praying aloud. You might have a look.
Hello. Jesus prayed in public, in front of other people.
Matthew 11:25-26
Luke 23:34
John 11:41-42
John 12:27-28
John 17:1-26
Jesus explains why he prayed openly in front of other people.
John 11:42
And I knew that thou hearest me always: but because of the people which stand by I said it, that they may believe that thou hast sent me.
Jesus prayed verbally because there were other people standing by.
"Is anyone among you sick? Let him call for the elders of the church, and let them pray over him, anointing him with oil in the name of the Lord. And the prayer of faith will save the one who is sick, and the Lord will raise him up. And if he has committed sins, he will be forgiven. Therefore, confess your sins to one another and pray for one another, that you may be healed. The prayer of a righteous person has great power as it is working." -- James 5:14-16
It appears that Christian intercessors may, indeed, gather to pray for an afflicted person. Do you believe they must do it silently, without communicating with one another?