Headphones are miniature loudspeakers that are placed over the ears and held in place by a band or wire worn over the head. They often feature cushioning to hold in sounds coming in or block outside sounds. Though airplane pilots are among the many professionals to use headphones on the job, most often headphones are thought of as auxiliary stereo equipment, used to listen to music without disturbing others, and in the production of music in the recording studio.

The first stereo headphones were invented in 1958 by John C. Koss, a Milwaukee-based jazz musician and audiophile. Before his time, headphones were used only in industry by telephone operators and the like. Koss's original idea consisted of a total stereo package: a small portable phonograph with attached speakers and his new headphones, designed with an audio engineer. When he took it to a hi-fi show in his hometown that...