Headphones are a pair of small loudspeaker drivers worn on or around the head over a user’s ears. They are electroacoustic transducers, which convert an electrical signal to a corresponding sound. Headphones let a single user listen to an audio source privately, in contrast to a loudspeaker, which emits sound into the open air for anyone nearby to hear. Headphones are also known as earspeakers, earphones, or, colloquially, cans. Circumaural (‘around the ear’) and supra-aural (‘over the ear’) headphones use a band over the top of the head to hold the speakers in place.