Echolocation- seeing by hearing / Is air moving in or out?

Why do bats have big ears? How do they see by hearing? Our class wanted to experience, how it must be for a bat , without hitting a stalactitie or bumping into a wall, how each bat hunts its food and locates its spot on the ceiling in the dark part of a cave? Our children discovered that it is not easy, we had one bat , who was blindfolded, the bat had to listen to a moth ( another student making sound from somewhere in the classroom ). The bat held his big ear ( a paper funnel that they made) and tried to eat that moth by following that sound. The children discovered that  it is not easy! Someone said, " I was bumping everywhere, and it was too dark, I don't want to be a bat".

Is air moving out of the cave or in?

When the wind blows: Is air moving throough the cave? The children experimented this by holding a piece of paper down. Some said  the paper was moving towards the twilight zone, hence air is flowing out , one student said, "her's was moving  into the cave "!