Why Does the Priest Say Certain Prayers Quietly During Mass?

A listener named Michael asks Father Dave about a prayer during Mass. "During the Liturgy of the Eucharist, there are certain things that the rubrics tell the priest to say quietly or inaudibly," Michael says. "I'm wondering why that would be, particularly because one of them says, 'By the mystery of this water and wine, may we come to share in the divinity of Christ, who humbled himself to share in our humanity.' That, to me, is like wow. That's where the lightning strikes, like the meeting of heaven and earth; that is the Mass. So why would that be said inaudibly?"