Now consider a bell in a tall tower. The bell rings with a ding.

The bell vibrates.

The vibration travels through the air to a girl's ear, far below. She can hear the bell.

The bell vibrates. The vibration travels through the air to the girl's ear. She hears the bell.

Now consider a dog behind a boy. The boy is not looking at the dog.

The dog lets out a loud woof.

Something in the dog's throat vibrates.

The vibration still travels through the air to the boy's ear. He can hear the bark.

The boy is not looking at the dog. The vibration still travels through the air to his ear, and he hears the bark.