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Headphones (also known as earphones, earbuds, stereophones, headsets, or by the slang term cans) are a pair of small loudspeakers, or less commonly a single speaker, with a way of holding them close to a user's ears and a means of connecting them to a stereophonic, monophonic or binaural audio-frequency signal source such as an audio amplifier, radio or CD player. In the context of telecommunication, the term headset is used to describe a combination of headphone and microphone used for two-way communication, for example with a telephone.
HistoryThe telephone earpiece such as the one pictured at the right was common around the turn of the 20th century. Sensitive headphones were the only way to listen to audio signals before amplifiers were developed. Very sensitive headphones such as those manufactured by Brandes (Fig.1) around 1919 were commonly used for early radio work.
ApplicationsHeadphones can be used both with fixed equipment such as CD or DVD players, home theater, personal computers and with portable devices (e.g. digital audio player/mp3 player, mobile phone, etc.). Some cordless headphones do not need to be connected via a wire, receiving a radio or infrared signal encoded using a radio or infrared transmission link, like FM, Bluetooth or Wi-Fi. These are actually made of powered receiver systems of which the headphone is only a component. Headphones are widely used for listening to audio sources for recreation. In the professional audio sector headphones are used in live situations by disc jockeys (DJ) and sound engineers for monitoring signal sources. In radio studios, DJs use a pair of headphones when talking to the microphone while the speakers are turned off, to eliminate acoustic feedback and monitor their own voice. In studio recordings, musicians and singers use headphones to play along to a backing track. Wired headphones are attached to an audio source. The most common connectors are 1/4" and 3.5 mm stereophonic jack plugs and sockets. The older 1/4" standard is used on professional equipment, and is often used on fixed equipment. Sony introduced the smaller and cheaper, and now widely-used, 3.5 mm stereo connector in 1979, adapting the older monophonic 3.5 mm connector for use with its Walkman portable stereo tape player. Adapters are available for converting between 1/4" and 3.5 mm devices.
Types of HeadphonesThere are many different types of headphone designs, with the listening situation and the needs of the listener determining what type of headphone will be used. Generally, headphone formfactors can be divided into four separate categories: Circumaural, supra-aural, earbud, and in-ear. Circumaural headphones have circular or ellipsoid earpads that fit around the ears. This type of headphone is commonly used in recording studios and among audio enthusiasts.
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