What electrostatic headphones are
What they are
A thin, electrostatically charged diaphram (typically a coated mylar membrane), is suspended between two perforated metal plates (electrodes). The electrical sound signal is applied to the electrodes creating an electrical field; depending on the polarity of the this field, the membrane is drawn towards one of the plates. Air is forced through the perforations; combined with a continuously changing electrical signal oscillating the membrane, a soundwave is generated.
There are two kinds of electrostatic headphones: electrostatic and electret. Electrostatic headphones work just like electrostatic loudspeakers, yet on a smaller scale. Electret headphones are are often confused for the better known electrostatic headphones, but which work on a different principle.
Typically electrostatic headphones are more expensive than dynamic, and are relatively rare. In addition, a special amplifier is required to amplify the signal to oscillate the membrane, which often requires electrical potentials in the range of 100 to 1000 Volts. Examples of electrostatic headphones are the Stax SR-007 Omega II, and the Sennheiser HE90 'Orpheus'.
Electret: Solid electrically insulating, or dielectric, material that has acquired a long-lasting electrostatic polarization. Electrets are produced by heating certain dielectric materials to a high temperature and then letting them cool while immersed in a strong electric field. An electret is an analog of a permanent magnet. Stax Ltd. for instance is a Japanese company that makes high end audio equipment and makes both electret and electrostatic headphones A headphone (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, WiFi) 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.
They can also be divided into two other categories being electrostatic and dynamic. There is also rumour that there will be a ribbon headphone available soon.
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 and some jurisdictions regulate the use of headphones while driving vehicles. Also, most European countries have imposed high penalties since 2002 on 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.
Headphones generally use a 3.5mm "mini pin" jack