Monday, April 19, 2010

Types of headphones

There are many different types of headphone designs, with the listening situation and the needs of the listener determining what type of headphone will be used. Generally, headphone formfactors can be divided into four separate categories: circumaural, supra-aural, earbud, and in-ear.

[edit] Earcup headphones

Earcup headphones

Earcup or on-ear headphones rest on the exterior of the ear and were the earliest headphone form designed.

The housing, or earcup, of an earcup headphone will be either open or closed. Open headphones, sometimes marketed as “open air” headphones, have an open grille on the back of the earcup, exposing the driver to the outside and allowing sound waves to propagate away from the ear freely. This backing type does not isolate the listener from outside sounds; in addition, sound through open headphones can be heard by others in the vicinity of the user. They usually have less distortion due to the lack of earcup resonance. Closed headphones have a sealed backing, which attenuates sound waves propagating away from the ear. As a result, listeners away from the headphones cannot hear the produced sound easily. In addition, sound from outside is attenuated by the sealed backing, providing a level of isolation to the listener. A sealed chamber is often claimed to have the negative effect of distorting sound in certain frequencies due to resonances within the earcup housing, however, bass frequencies are stronger in a sealed chamber headphone design.

[edit] Circumaural

Circumaural headphones have large pads that surround the outer ear.

Circumaural headphones (sometimes called full size headphones) have circular or ellipsoid earpads that completely surround the ears. Because these headphones completely surround the ear, circumaural headphones can be designed to fully seal against the head to keep out external noise. Because the earpads must enclose the ear, circumaural headphones are often larger in size and tend to weigh more, making them somewhat less portable, but their size also allows for a larger driver.

This type of headphone is commonly used in recording studios, by audio enthusiasts, or by people who must be able to comfortably wear headphones continuously for many hours.

[edit] Supra-aural

A pair of supra-aural headphones.

Supra-aural headphones have pads that sit atop of the ears, rather than around them. They were commonly bundled with personal stereos during the 1980s. This type of headphone generally tends to be smaller and more lightweight than circumaural headphones. Supra-aural foam pads must press down on the earlobes with some force to hold the headphones in place, so they can cause severe earlobe pain when worn for many hours at a time.

[edit] In-ear headphones

[edit] Earbuds

Earbuds / earphones

Earbuds or earphones are headphones of a smaller size that are placed directly outside of the ear canal, but without fully enveloping it. They are generally inexpensive and are favored for their portability and convenience. However, due to their inability to provide isolation, they are not capable of delivering the same dynamic range offered by many full-sized headphones and canalphones for a given volume level. As a result, they are often used at higher volumes in order to drown out noise from the user's surroundings, which increases the risk of hearing-loss.[2] During the 1990s and 2000s, earbuds became a common type bundled with personal music devices.

[edit] Canalphones

Canalphones extend into the ear canal, facilitating greater dynamic range than earbuds as well as isolation from outside noise.

Canalphones (also known as in-ear monitors, or IEMs) are earphones that are inserted directly into the ear canal. Canalphones offer portability similar to earbuds, and also act as earplugs to block out environmental noise. There are two main types of IEMs: universal and custom. Universal canalphones provide one or more stock sleeve size(s) to fit various ear canals, which are commonly made out of silicone rubber, elastomer, or foam, for noise isolation. Universal canalphones are typically marketed to casual listeners and are relatively inexpensive, though some offer very high audio quality.

Custom canalphones are fitted to individuals. Castings of the ear canals are made, usually by an audiologist. The manufacturer uses the castings to create custom-molded silicone rubber or elastomer plugs that provide added comfort and noise isolation. Because of the individualized labor involved, custom IEMs are more expensive than universal IEMs.

[edit] Headset

A typical example of a headset used for voice chats.

A headset is a headphone combined with a microphone. Headsets provide the equivalent functionality of a telephone handset with hands-free operation. Headsets typically have only one speaker like a telephone, but also come with speakers for both ears.[3] They have many uses including in Call centres and other telephone-intensive jobs and for personal use at the computer to facilitate comfortable simultaneous conversation and typing.

Headsets can come in single-earpiece and double-earpiece designs. Single-earpiece headsets are known as monaural headsets. However, double-earpiece headsets come in both stereo type (two channels of audio signal, one for each earpiece) or binaural type (the same audio channel for both ear-pieces).

The microphone arm of headsets comes in external microphone type and voicetube type. External microphone designs have the microphone housed in the front end of the microphone arm, inside a microphone capsule. Voicetube designs are also called internal microphone design, and have the microphone housed near ear-piece. The sound travels through the tube to the hidden microphone.

[edit] Telephone headsets

Telephone headsets connect to a fixed-line telephone system. A telephone headset functions by replacing the handset of a telephone. All telephone headsets come in a standard 4P4C commonly called an RJ-9 connector.

For older models of telephones, the headset microphone impedance is different from that of the original handset, requiring a telephone amplifier to pair with the telephone headset. A telephone amplifier provides basic pin-alignment similar to a telephone headset adaptor, but it also offers sound amplification for the microphone as well as the loudspeakers. Most models of telephone amplifiers offer volume control for loudspeaker as well as microphone, mute function and headset/handset switching. Telephone amplifiers are powered through batteries or AC adaptors.

[edit] Technology

A typical moving-coil headphone transducer

Headphone transducers employ one or more of several methods of sound reproduction.

[edit] Moving-coil

The moving coil driver, more commonly referred to as a "dynamic" driver is the most common type used in headphones. The operating principle consists of a stationary magnetic element affixed to the frame of the headphone which sets up a static magnetic field. The magnetic element in headphones is typically composed of ferrite or neodymium. The diaphragm, typically fabricated from lightweight, high stiffness to mass ratio cellulose, polymer, carbon material, or the like, is attached to a coil of wire (voice coil) which is immersed in the static magnetic field of the stationary magnet. The diaphragm is actuated by the attached voice coil, when an audio current is passed through the coil. The alternating magnetic field produced by the current through the coil reacts against the static magnetic field in turn, causing the coil and attached diaphragm to move the air, thus producing sound. Modern moving-coil headphone drivers are derived from microphone capsule technology.

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