Guys, guys (and lady). Being heard by 5,000 people in open air is nothing. All you need to know is a little history, especially about one of the most famous itinerant, open air preachers in Western history: George Whitefield. In one (possibly exaggerated) case Whitefield was said to speak to a crowd of 100,000 people in Ireland! But, at the least, the ever-scientific Benjamin Franklin (who was a friend of Whitefield) was so impressed by the power of Whitefield's voice and how far it carried that he calculated an estimate of how many people could hear him at once. From Franklin's own autobiography (from
chapter 8):
"
He had a loud and clear voice, and articulated his words and sentences so perfectly, that he might be heard and understood at a great distance, especially as his auditories, however numerous, observ'd the most exact silence. He preach'd one evening from the top of the Court-house steps, which are in the middle of Market-street, and on the west side of Second-street, which crosses it at right angles.
Both streets were fill'd with his hearers to a considerable distance. Being among the hindmost in Market-street,
I had the curiosity to learn how far he could be heard, by retiring backwards down the street towards the river; and I found his voice distinct till I came near Front-street, when some noise in that street obscur'd it. Imagining then a semi-circle, of which my distance should be the radius, and that it were fill'd with auditors, to each of whom I allow'd two square feet,
I computed that he might well be heard by more than thirty thousand. This reconcil'd me to
the newspaper accounts of his having preach'd to twenty-five thousand people in the fields, and to the
ancient histories of generals haranguing whole armies, of which I had sometimes doubted."
Over 30,000 people could hear Whitefield at once! Now that's downright impressive! If you want to study how far voices can carry study the great open air preachers of the past (and it is interesting also how Franklin mentions military generals talking to their entire army at once in ancient histories). I wrote a paper for my University's Puritan Literature class on the life of George Whitefield which has some additional details on the numbers of the crowds that he spoke to:
The Life of George Whitefield.