Headphone, also known as tereophones, headsets or colloquially cans, is a pair of small loudspeakers, or a conversion unit. It accepts the a signal source such as an audio amplifier, radio or CD player and with a way of holding them close to a user’s ears. Earphone generally can separate from media players, using a plug connection. Earphone can stop the noise of the surrounding environment, which is helpful for people who want to listen to audio alone.

To begin with, earphone was use for telephone and radio. But with the development of the portable electronic communication devices, earphone is used for mobile phone, walkman radio, or other portable video and digital music player etc.

Headphone is useful and comfortable, but you have to use is appropriately.

Please don’t use headphones at a sufficiently high volume level because it may cause temporary or permanent hearing impairment or deafness due to an effect called “masking.” You should make the headphone volume compete with the background noise, especially in excessively loud places such as subway stations, aircraft, and large crowds.

Some manufacturers of portable music devices have attempted to introduce safety circuitry that limited output volume or warned the user when dangerous volume was being used, but the concept has been rejected by most of the buying public, which favors the personal choice of high volume.

Other risks arise from the reduced awareness of external sounds, usually limiting the use of earphones to a single ear. The complete isolation from outside noise can be a hazard in itself, as a user could miss the sound of a car horn and walk into traffic with fatal consequences. Losing situational awareness can also lead to theft, particularly in busy environments where bumping into another person would be ignored, e.g., subway stations.

Motorcycle and other power-sport riders benefit by wearing foam earplugs when legal to do so to avoid excessive road, engine and wind noise, but their ability to hear music and intercom speech is actually enhanced when doing so.  At very high sound pressure levels, muscles in the ear tighten the tympanic membrane and this leads to a small change in the geometry of the ossicles and stirrup that results in lower transfer of force to the oval window of the inner ear.

Since earplugs reduce the noise in the auditory canal, this protective mechanism is less likely to trigger, and full sensitivity of the ear is maintained. With normal sensitivity, a listener has excellent hearing while listening to helmet speakers through the earplugs. This technique allows excellent hearing of speech, music and most external sounds at sustainable levels without hearing damage.

When you do exercise, listening to music through headphones can be dangerous too. Blood may be diverted from the ears to the limbs leaving the inner ear more vulnerable to damage from loud sound. A Finnish study recommended that exercisers should set their headphone volumes to half of their normal loudness and only use them for a half hour.