Headphones

From Wikipedia, the free encyclopedia

For other uses, see Headphones (disambiguation).

Headphones (also known as earphones, earbuds, stereophones, headsets, or  by the slang term cans) are  a pair of transducers that receive an  electrical signal from a media player or  receiver and  use speakers placed in close proximity to the ears (hence the name earphone) to convert the signal into audible sound waves. In the context of telecommunication, the term headset is  also commonly understood to refer to a combination of headphones and  microphone used for two-way communication, for example with a mobile phone.

Contents 1 History 2 Applications 3 Benefits and  limitations 4 Dangers and  volume solutions 5 Types of headphones 5.1 Circumaural 5.2 Supra-aural 5.3 Earbuds/Earphones 5.4 Canalphones 6 Driver types 6.1 Dynamic 6.2 Electrostatic 6.3 Balanced armature 7 Backing type 7.1 Open 7.2 Closed 8 Methods of wearing headphones 8.1 Over the head 8.2 Behind the head 8.3 Clip 8.4 In-ear 8.5 Under the chin 9 See also 10 References 11 External links

[edit] History

Headphones date from the beginnings of the history of the telephone and  the radio. The weak electrical signals of the early instruments were enough to operate only headphones audibly. Beyerdynamic is  considered to have  officially invented headphones in the late 1930s, and  was the first company to market headphones to the public.^[1][2]

[edit] Applications

Headphones are  normally detachable, using a jack plug. Typical products to which they are  attached include the walkman, mobile phone, CD player, Minidisc player, digital audio player, (mp3 player), and  personal computer. Headphones can also be used with full-size stereo components. Some headphone units are  self-contained, incorporating a radio receiver. Other headphones are  cordless, using radio (for example analogue FM, digital Bluetooth, Wi-Fi or  infrared) signals to receive signals from a base unit.

Another application is  in the professional audio sector. Here, headphones are  used in live-situations by DJ's and  sound engineers for monitoring channels independently from what the public hears. an  effect can also be previewed this way. In radio-studios diskjockeys use a pair of headphones when talking in the microphone while the speakers are  turned off, for reduced feedback and  monitoring of their own voice. In studio-recordings, musicians and  singers use headphones to play along a backing track. These headphones tend to be of better quality than 'normal' headphones.

The two common connectors are  1/4" and  3.5 mm plug. Headphones designed for home stereo systems and  recording studios use the older 1/4" connector. Sony introduced the 3.5mm connector in 1979, adapting the older monophonic 3.5mm connector for use with its Walkman personal stereo. Advantages of the smaller connector include lower bulk, weight and  cost. This smaller connector is  more prevalent today due to the popularity of portable music devices, although aftermarket headphones sometimes include an  adapter for compatibility with the larger connector. Please note that in the professional world, only 1/4" is  used. Therefore, professional phones are  actually 1/4" oriented and  always include an  adapter to 3.5 mm.

[ and  limitations">edit] Benefits and  limitations

Headphones may be used to prevent other people from hearing the sound either for privacy or  to prevent disturbance, as in listening in a public library. They can also provide a level of sound quality that could only be matched by speakers costing a great deal more. This is  especially true in the bass (low frequency) region, where loudspeaker-listening room interactions normally cause resonant modes so that even with the best speakers a listener in a given place hears some bass notes too loudly and  others too softly. Good headphones, with a good seal to the ear can have  an extremely flat low-frequency response down to 20 Hz within 3dB (though claims such as 'frequency response 4 Hz to 20 kHz' are  just marketing hype based on the fact that the headphone has some output at 4 Hz; response at frequencies lower than 20 Hz is  however very small). Headphones of the 'closed back' type are  also used to exclude external sounds, particularly in sound recording studios and  in noisy environments. Headphones can also be useful for videogames that use 3D positional audio, allowing players to better judge the position of an  offscreen sound (such as the footsteps of an  opponent).

Although modern headphones are  very widely sold and  used for listening to stereo, especially since the invention of the Walkman, they are  fundamentally unsuited to such use. This is  why they usually produce the disconcerting effect of sound coming from the middle of the listener's head, with unnaturally isolated sounds occasionally appearing predominantly in one ear, giving the impression that the other has suddenly gone deaf. This is  because stereo recordings represent the position of each sound by large amplitude differences between two channels intended for reproduction through a pair of loudspeakers. When the sounds from the two speakers mix at each ear they create the phase difference which our brain uses to locate direction (at least below 2 kHz). Binaural recordings use a different microphone technique to encode direction directly as phase, with very little amplitude difference (except above 2 kHz) often using a dummy head, and  can produce a surprisingly life-like spatial impression through headphones. Commercial recordings almost always use stereo recording though, because historically loudspeaker listening was more  popular than headphone listening. it  is possible to improve the spatial effect from stereo on headphones by using frequency-dependent cross-feed between the channels, or  better still a Blumlein shuffler (custom EQ employed to augment the low-frequency content of the difference information in a stereo signal) though this is  rarely done. While cross-feed can reduce the feeling of deafness in one ear, only the use of a dummy head when the actual recording is  done, with artificial pinnae can convincingly take away the middle-of-the-head effect. Optimal sound can only be achieved when the dummy-head matches the listener's head, since pinnae vary greatly in size and  shape.

Headphones can have  an ergonomic benefit over the traditional handset at office desks. They save space and  many new models are  wireless. They also allow call center agents to maintain good posture instead of tilting their head sideways to cradle a handset. They are  also used in professional sound editing, so that more  than one person can work on an  audio track without interfering with another.

[ and  volume solutions">edit] Dangers and  volume solutions

Using headphones at a sufficiently high volume level can cause temporary or  permanent hearing impairment or  deafness due to an  effect called masking. The headphone volume has to compete with the background noise, especially in excessively loud places such as subway stations, airplanes, and  large crowds. This leads to the disappearance of the normal pain associated with higher levels of volumes, and  extended periods of the excessively loud volume is  extremely damaging. 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 personal choice of high volume. Koss introduced the "Safelite" line of cassette players in 1983 with such a warning light. The line was discontinued two years later for lack of interest.

In recent years, interest has once again  focused on protecting hearing, and  companies have  responded. Sony's AVLS feature corrects differences in track volumes as they are  being played, and  Apple's Sound Check normalizes the peak volumes of selected tracks in iTunes. Also, one may manipulate the volume tags, or  Replay Gain, of MP3s; this method must be manually done by the user using 3rd-party software, but is  regarded to provide better consistency than the above options. Also of note, the French government has imposed a limit on all music players sold in the country: they may not be capable of producing more  than 100 dbA (the threshold of hearing damage during extended listening is  80 dB, and  the threshold of pain, or  of immediate hearing loss, is  130 dB). Many decry this as an  infringement on personal choice, and  use 3rd-party options to reverse the software volume caps placed on such devices. Others welcome the government's pro-health stance.

Other risks arise from the reduced awareness of external sounds — some jurisdictions regulate the use of headphones while driving vehicles, usually limiting the use of earphones to a single ear.

Canalphones (which sit directly in the ear canal, much as earplugs do) are  generally believed to be safer than open-air headphones for use in noisy environments. The reason for this is  that much of the external noise which is  usually heard while using earphones/headphones is  blocked out by canalphones, therefore allowing the user to listen at lower volumes without having to turn up the listening device (possibly to unsafe levels) to compete with background noise (a passive counterpart to active noise cancellers, which use circuitry and  destructive wave interference to attenuate sound). Manufacturers of canalphones quote that their products reach an  isolation level of -30-40 dB, while noise cancellers isolate by a degree of -15-20 dB. Closed and  noise-cancelling headphones can have  a similar effect, although sound attenuation of the latter is  usually limited in frequency range and  amplitude: closed headphones do not isolate low frequency sounds very well, and  noise cancellers do not attempt to attenuate high-pitched sounds.

[edit] Types of headphones

In descending order of size:

[edit] Circumaural

Circumaural headphones have  pads that go around the ears, usually very large and  very comfortable. This is  the type typically used in recording studios and  among audiophiles. Examples include: AKG K501, Audio-Technica ATH-A900, Beyerdynamic DT880, Sennheiser HD650, Sony MDR-V6, Koss Pro/4AA, Ultrasone HFI-2200 ULE.

[edit] Supra-aural

Supra-aural headphones have  pads that go on top of the ears. They were commonly bundled with personal stereos during the 1980s. Examples include: Grado SR-60, Koss Porta Pro, Sennheiser PX-100, Ultrasone iCans, Bose QuietComfort 3.

[edit] Earbuds/Earphones

Earbuds (American English) or  Earphones (British English) are  small headphones 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 precision and  range of sound offered by many full-sized headphones and  canalphones. 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.^[3]

During the 1990s, they became the most common type bundled with personal music devices. For example, the distinctive white headphones included with the iPod are  earbuds.

[edit] Canalphones

Canalphones, also known as in-ear monitors, are  earbuds that sit directly inside the ear canal. They offer portability similar to earbuds but with greater sound isolation, and  often deep bass response.

There are  two main types of canalphones — universal and  custom. Universal canalphones provide one or  more stock sizes of cushions to fit various ear canals (which are  commonly made out of silicone rubber, elastomer, or  foam). 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 greater comfort and  "closed-canal, closed-air" noise isolation (a passive noise cancellation principle that does not require use of batteries). Because of the individualized labor involved, custom canalphones are  far more  expensive.

[edit] Driver types

The drivers are  the primary provider of sound in the headphones.

[edit] Dynamic

The dynamic driver is  the most common type used in headphones. This 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 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 flowing 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 dynamic headphone drivers were derived from dynamic microphone capsules.

[edit] Electrostatic

A thin, electrostatically charged diaphragm (typically a coated PET film membrane), is  suspended between two perforated metal plates (electrodes). The electrical sound signal is  applied to the electrodes creating an  electrical field; depending on the polarity of this field, the membrane is  drawn towards one of the plates. Air is  forced through the perforations; combined with a continuously changing electrical signal oscillating the membrane, a soundwave is  generated.

Typically electrostatic headphones are  more expensive than dynamic, and  are relatively rare. In addition, a special amplifier is  required to amplify the signal to oscillate the membrane, which often requires electrical potentials in the range of 100 to 1000 Volts.

Examples of electrostatic headphones are  the Koss ESP/950, Stax SR-007 Omega II, and  the Sennheiser HE90 "Orpheus".

[edit] Balanced armature

Usually used only in canalphones (due to their diminutive size and  low impedance), such as Etymotic, Shure, Sensaphonics, and  Ultimate Ears. They generally are  limited at the extremes of the hearing spectrum (>16 kilohertz, <50 hertz) and  require a seal more  than other types of drivers to deliver their full potential. Some canalphones, like the Ultimate Ears super.fi 5EB combine an  armature driver (for high frequencies) and  a small dynamic driver (for low frequencies), for the benefit of lower costs. For the higher-end models, such as super.fi 5 Pro and  the Shure E5C, dual balanced armature drivers were utilized for a more  balanced picture. Highest-end models such as the Ultimate Ears UE-10pro and  Westone ES3 employs triple balanced armature drivers with a view to enhance the sound towards perfection. However, multiple-drivers earphones tend to have  the problem of inaccurate spacing and  emphasize in the bass department, thus losing fidelity to a certain extent. This is  compensated by added details and  a broader soundstage.

Besides the construction of the actual sound producer, the amount of "load" or  impedance on the line is  an important differentiating factor among headphone design. Many common headphones using a dynamic driver resting on or  slightly in the ear have  32 Ohms impedance. Smaller, in-the-ear types may have  an impedance as low as 16 or  11 Ohms. "Studio" and  noise-reducing headphones tend to have  much higher impedances, ranging from 300 in some cases to as high as 5000 Ohms in other. Often portable devices designed to work with low-impedance headphones are  unable to drive high-impedance headphones to high levels of sound.

[edit] Backing type

[edit] Open

Open headphones (sometimes marketed as "open air" headphones) have  an open grille on the back of the driver, exposing the driver to the outside, and  allowing the soundwaves 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 easily heard by others in the vicinity of the user (not always a desirable quality). They, however, usually have  a more  expansive soundstage (due to the lack of resonance) and  more tightly controlled sound reproduction; most audiophile-quality headphones, like the ones listed below, are  open headphones.

Examples of open headphones: AKG K-501, Grado RS-1, Sennheiser HD-650, Koss UR-5.

[edit] Closed

Closed headphones have  a sealed backing, which attenuates soundwaves propagating in the direction away from the ear. As a result, listeners away from the headphones cannot hear the produced sound easily. In addition, extra-soundwaves are  attenuated due to the sealed backing, providing a level of isolation to the listener (typically a 10dB decrease in outside sounds). Their sealed chamber generally has the added negative effect of reducing soundstage and  providing "boomier", less  controlled bass, making them skew lower in price and  high-end quality than open headphones.

Examples of closed headphones: AKG K271S, Audio Technica ATH-A900, Sennheiser HD-280 Pro, Sony MDR-V6, Koss Pro/4AA, Ultrasone HFI-550, Beyerdynamic DT-100.

[edit] Methods of wearing headphones

[edit] Over the head

The traditional style of headphones has a band or  bands over the top of the head. This is  especially prevalent for heavier headphones such as circum-aural designs, which would otherwise slip downward due to their weight.

[edit] Behind the head

Designs with the headband behind the head are  usually used in portable supra-aural headphones. They do not disturb one's hair like an  over-the-head headband does, and  can be worn with hats, etc. However, they can be uncomfortable when using them in lying on one's back or  when sitting on a chair with headrest. This now-common style, sometimes referred to as "street-style," was popularized by Sony.

[edit] Clip

The earpiece is  secured with a clip that wraps around the base of the pinnae (outer ear), similar to eyeglass temples (thus potentially uncomfortable for anybody wearing eyeglasses). Usually used with earbuds, but also sometimes used with supra-aural headphones or  canalphones.

[edit] In-ear

Earbuds and  canalphones sit on the concha of the pinnae or  directly in the ear canal.

[edit] Under the chin

This style is  very rare in consumer headphones, using a U-shaped tension band suspended beneath the chin to hold transducers in the ears, similar to the design of stethoscopes. it  was sometimes used in inexpensive airline headphones, although Sennheiser had a cordless model on the market for a short period.

[edit] See also

• Noise-cancelling headphone
• Wireless headphones
• Loudspeaker
• Subwoofer (Stereo separation)
• Microphone
• Headphone amplifier
• Head-fi

[edit] References

1. ^ http://www.beyerdynamic.com/cms/History.687.98.html?L=0
2. ^ http://www.beyerdynamic.co.uk/brochures/HIFI_E_2002.pdf#search='beyerdynamic%20history'
3. ^ http://www.ear-hearing.com/pt/re/earhearing/abstract.00003446-200412000-00001.htm

[edit] External links

Wikimedia Commons has media related to: Headphones

• The Audio Circuit - Information on and  user reviews of loudspeakers, headphones, amplifiers, and  playback equipment
• Types of Headphones, Koss website
• Headphone Gallery & Archive - Database of Headphone Specifications and  Images
• Headwize: A Resource Site for Headphones and  Headphone Listening
• HeadphoneReviews.org-A sister site of the Head-Fi forums; reviewers rate their headphones on criteria like bass extension/quality, comfort, soundstage, etc. No reviews of common, low-cost headphones.
• Head-Case: Ad and  Commercial Free, just-the-facts Forum Site for Headphone Fans.
• Headphonesguru : a resource site for headphones - tests, projects, DIY, articles, products, links.
• Head-Fi: Covering Headphones, Earphones and  Portable Audio