A horn is a tapered sound guide designed to provide an acoustic impedance match between a sound source and free air. This has the effect of maximizing the efficiency with which sound waves from the particular source are transferred to the air. Conversely, a horn can be used at the receiving end to optimize the transfer of sound from the air to a receiver.

Acoustic horns are used in:

Loudspeakers are often built into horn-shaped enclosures or use horns. Most often the higher-frequency elements (tweeters; midrange) use horns, sometimes with acoustic diffraction lenses to spread the sound waves in a horizontal pattern at ear-level. An audio driver (e.g., a speaker cone or dome) is mounted at the small, inner end. Horn loudspeakers are very efficient, but have a sharp cutoff frequency, depending on their size, with little sound output below. Bass sounds are usually produced by conventional speaker cones, since a (straight or folded) horn sufficient to reproduce 20 Hz can be about 12 ft. (4 meters) long, except when a building, ground surface, or room itself is considered as part of the horn.

Adam Richard Wiles (born 17 January 1984), better known by his stage name Calvin Harris, is a Scottish DJ, singer, songwriter, and record producer. His gold-selling debut album, I Created Disco, was released in 2007 and contained the top ten singles "Acceptable in the 80s" and "The Girls". His second studio album, Ready for the Weekend (2009), reached number one in the UK Album Chart and includes the chart-topper "I'm Not Alone", the UK top five hit "Ready for the Weekend", and the singles "Flashback" and "You Used to Hold Me".

A remix album titled L.E.D. Festival was released in July 2010 as a free album in the August issue of Mixmag. Harris is currently working on his third studio album—due for release in 2012—which has produced the singles "Awooga", "Bounce", "Feel So Close", and "Let's Go". He has written and produced records for other recording artists including Kylie Minogue, Sophie Ellis-Bextor, Dizzee Rascal, Rihanna (on the international chart topper "We Found Love"), and Kesha.