Anyone who enjoys an mp3 or CD player, likes to watch movies on long flights or even needs to talk on their phone while still having their hands free uses earphones. They are small, portable and most importantly, quite comfortable. This is in no small part due to the materials which earphones of which they are made.
Hard plastic is used for the outer shell of the earphone and serves to protect the sensitive inner workings of the device.
Inside each earphone bud is a small aluminum coil that acts as a type of transducer, turning the raw data into audible sound.
Newer earphones use rubber around the earphone speaker. This is used to add extra comfort for the user.
Earphones use wire to connect not just the earphone speakers to small chips inside the earphone bud, but also to connect the earphones to the TRS connector.
Many TRS connectors, or "audio jacks," are made of copper. Copper is an excellent conductor for electricity.