Headphones
Headphones (also known as earphone, stereophone, headset) is a transducer that receives an electrical signal from a media player or receiver and uses speakers placed in close proximity to the ears (hence the name earphone) to convert the signal into audible sound waves.
They are normally detachable, using a jack plug. Typical products to which they are attached include the walkman, mobile phone, CD player, MP3 player, and personal computer. Some headphone units are self-contained, incorporating a radio receiver. Other headphones are cordless, using radio (e.g. analogue FM, digital bluetooth) or infrared signals to communicate with a "base" unit.
Headphones may be used to prevent other people from hearing the sound either for privacy or to protect others. They are also used to exclude external sounds, particularly in sound recording studios and in noisy environments.
Generally headphones can be divided into two categories, closed and open. Closed headphones isolate background noise better, while open headphones offer a more "open" sound. Typically open headphones will sound better than similarly priced closed headphones.
Using headphones at a sufficiently high volume level causes temporary or permanent hearing impairment or deafness. Other risks arise from the reduced awareness of external sounds — some jurisdictions regulate the use of headphones while driving vehicles. Also, most European countries have imposed high penalties since 2002 for drivers not using a headset while operating a mobile phone in a car, to ensure that drivers keep their hands on the vehicle's controls.