Earphones

Earphones, sometime also referred to as earbuds, headphones or stereophones, are electronic devices that act as miniature speakers. Compatible with a music system, walkman, discman, television, MP3 player or personal computer, these gadgets are composed of a connector at one end that plugs into the player and tiny speakers at the other end that are inserted into the user’s ears. Earphones began to be used in the early part of the twentieth century, ever since telephony and radio became common. Some audio signals from those primitive machines could be only detected by sensitive earphones.

Earphones are of many types. Canalphones, which are also called Interruptible Foldback Systems (IFS), extend into the ear canal, thus virtually eliminating outside noise. Earbuds generally reside outside the ear canal and offer good sound, but do not eliminate outside noise. The portion of the earphone entering the ear is made of foam, elastomer or silicone rubber. Sometimes canalphones are customized as per the user specifications.

The technology used in earphones is either dynamic or electrostatic. In dynamic earphones, a static magnetic field is generated by a magnetic element connected to the frame of the earphone. An alternating magnetic field created by the flowing current interacts with the static field to produce sound through the movement of the coil and the diaphragm. In electrostatic earphones, a charged diaphragm is located between two electrodes. When current is passed through the electrodes, a magnetic field is created that causes the diaphragm to move and give rise to the sound output.