eli5: How a simple cone can amplify the sound?

Question

That wouldn’t require some way to add energy to the sound?

In: 10

Answer 1

If we’re talking about loudspeakers:

Imagine you’re running at high speed into a group of people. They see you and they move slightly to get out of your way.

Now imagine the people are constrained by the walls of a hallway. They can’t get out of the way. You crash into them, transferring the full energy of your speed.

A speaker cone (horn) prevents the air from getting out of the way of the speaker’s moving membrane.

/u/TheJeeronian’s comment provides a more accurate and detailed answer.