Headphones are used not only for private entertainment, but also for professional monitoring. The most common uses and for field recording where a loudspeakers would be impractical or for musicians in the studio who need to hear each other or previously recorded tracks for overdubbing.

Four types of headphones are common:

Closed Headphones

The first is the Enclosed (Closed, Closed Back or Isolating) type. The enclosed headphone seals outside sound out and inside sound in. It is best used in noisy environments, as it has difficulty consistently reproducing bass frequencies since the seal against the head varies with pressure, hair and eyeglasses.

Open Headphones

The second is called Open (Open-Aire, Open Back, Vented) type. The Open headphone is usually more accurate, consistent and lower in cost for the same performance as an Enclosed headphone. Comfort is usually higher since less pressure is required against the ear. Musicians often prefer them when playing or singing since they can hear some natural sound through them.

Voice Headphones

The third type could use either Open or Enclosed but is designed for voice communications, intercom, or language lab use. The frequency response is tailored for clear voice reproduction and not for music.

In-ear earphones

The forth is in-ear earphones. Used when talent is either on-camera or performing and does not want the phone visible. These either have the transducer at the ear like a hearing aid or clipped behind the neck with a clear plastic tube and earmold in the ear canal. In a pinch, consumer 'earbuds' may be used in this application.

Factors to consider when buying headphones.

The higher the price, the wider the frequency response and the closer the two sides will match each other. The effect of headphones is to exaggerate frequency response and stereo width, making them hard to use for critical esthetic judgements. Chances are the more boring a pair of headphones sounds, the more they will sound like speakers.

Watch out for impedance and power handling, most modern mixers and recorders require headphones to have between 30 and 90 ohms impedance, a higher impedance will work, but at reduced volume. Headphone amplifiers are a good idea since most built-in headphone amplifiers are quite low in quality.