Applied Science | How a horn amplifies sound (hint: Impedance matching) @AppliedScience | Uploaded 9 years ago | Updated 1 hour ago
A horn-shaped speaker is louder than an equivalent speaker without the horn. This fact doesn't violate physics because the horn is acting as a matching device between the speaker and the air around it.

Photo Credit for phonograph: Norman Bruderhofer, Collection of John Lampert-Hopkins