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Headphones are a pair of small loudspeaker drivers worn on or around the head over a user's ears. They are electroacoustic transducers, which convert an
electrical signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing ...
to a corresponding
sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by ...
. Headphones let a single user listen to an audio source privately, in contrast to a
loudspeaker A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or ...
, which emits sound into the open air for anyone nearby to hear. Headphones are also known as earspeakers, earphones or, colloquially, cans. Circumaural ('around the ear') and supra-aural ('over the ear') headphones use a band over the top of the head to hold the speakers in place. Another type, known as earbuds or earpieces consist of individual units that plug into the user's ear canal. A third type are bone conduction headphones, which typically wrap around the back of the head and rest in front of the ear canal, leaving the ear canal open. In the context of
telecommunication Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that ...
, a headset is a combination of headphone and
microphone A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and publ ...
. Headphones connect to a signal source such as an audio
amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost t ...
,
radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30  hertz (Hz) and 300  gigahertz (GHz). They are generated by an electronic device called a tr ...
, CD player,
portable media player A portable media player (PMP) (also including the related digital audio player (DAP)) is a portable consumer electronics device capable of storing and playing digital media such as audio, images, and video files. The data is typically stored o ...
,
mobile phone A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link whi ...
,
video game console A video game console is an electronic device that outputs a video signal or image to display a video game that can be played with a game controller. These may be home consoles, which are generally placed in a permanent location connected to ...
, or electronic musical instrument, either directly using a cord, or using
wireless Wireless communication (or just wireless, when the context allows) is the transfer of information between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most ...
technology such as
Bluetooth Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is limi ...
, DECT or
FM radio FM broadcasting is a method of radio broadcasting using frequency modulation (FM). Invented in 1933 by American engineer Edwin Armstrong, wide-band FM is used worldwide to provide high fidelity sound over broadcast radio. FM broadcasting is cap ...
. The first headphones were developed in the late 19th century for use by telephone operators, to keep their hands free. Initially the audio quality was mediocre and a step forward was the invention of high fidelity headphones. Headphones exhibit a range of different audio reproduction quality capabilities. Headsets designed for telephone use typically cannot reproduce sound with the high fidelity of expensive units designed for music listening by audiophiles. Headphones that use cables typically have either a 1/4 inch (6.35mm) or 1/8 inch (3.5mm) phone jack for plugging the headphones into the audio source. Some stereo earbuds are wireless, using
Bluetooth Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is limi ...
connectivity to transmit the audio signal by radio waves from source devices like cellphones and digital players. As a result of the Walkman effect, beginning in the 1980s, headphones started to be used in public places such as sidewalks, grocery stores, and public transit. Headphones are also used by people in various professional contexts, such as
audio engineer An audio engineer (also known as a sound engineer or recording engineer) helps to produce a recording or a live performance, balancing and adjusting sound sources using equalization, dynamics processing and audio effects, mixing, reproduction ...
s mixing sound for live concerts or
sound recording Sound recording and reproduction is the electrical, mechanical, electronic, or digital inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording ...
s and DJs, who use headphones to cue up the next song without the audience hearing, aircraft pilots and call center employees. The latter two types of employees use headphones with an integrated microphone.


History

Headphones grew out of the need to free up a person's hands when operating a telephone. There were several iterative products that were predecessors to the "hands-free" headphones. By the 1890s the first device that is unmistakably a headphone was made by a British company called Electrophone, which created a system allowing their customers to connect into live feeds of performances at theaters and opera houses across London. Subscribers to the service could listen to the performance through a pair of massive earphones that connected below the chin, held by a long rod. French engineer
Ernest Mercadier Ernest is a given name derived from Germanic word ''ernst'', meaning "serious". Notable people and fictional characters with the name include: People *Archduke Ernest of Austria (1553–1595), son of Maximilian II, Holy Roman Emperor *Ernest, M ...
patented a set of in-ear headphones in 1891, Mercadier was awarded U.S. Patent No. 454,138 for “improvements in telephone-receivers…which shall be light enough to be carried while in use on the head of the operator.” Nathaniel Baldwin of Utah in 1910 invented a prototype telephone headset due to his inability to hear sermons during Sunday service. He offered it for testing to the US Navy, which promptly ordered 100 from Baldwin. Wireless Specialty Apparatus Co., in partnership with Baldwin Radio Company, set up a manufacturing facility in Utah to fulfill orders. His innovations were the basis of “sound-powered” telephones or phones that required no electricity, which were used during World War II. Headphones originated from the telephone receiver earpiece, and were the only way to listen to electrical audio signals before amplifiers were developed. These early headphones used moving iron drivers, with either single-ended or balanced armatures. The common single-ended type used voice coils wound around the poles of a permanent magnet, which were positioned close to a flexible steel diaphragm. The audio current through the coils varied the magnetic field of the magnet, exerting a varying force on the diaphragm, causing it to vibrate, creating sound waves. The requirement for high sensitivity meant that no damping was used, so the frequency response of the diaphragm had large peaks due to resonance, resulting in poor sound quality. These early models lacked padding, and were often uncomfortable to wear for long periods. Their impedance varied; headphones used in
telegraph Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas ...
and telephone work had an impedance of 75 
ohm Ohm (symbol Ω) is a unit of electrical resistance named after Georg Ohm. Ohm or OHM may also refer to: People * Georg Ohm (1789–1854), German physicist and namesake of the term ''ohm'' * Germán Ohm (born 1936), Mexican boxer * Jörg Ohm (bor ...
s. Those used with early wireless radio had more turns of finer wire to increase sensitivity. Impedance of 1,000 to 2,000 ohms was common, which suited both crystal sets and triode receivers. Some very sensitive headphones, such as those manufactured by Brandes around 1919, were commonly used for early radio work. In early powered radios, the headphone was part of the
vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as ...
's plate circuit and carried dangerous voltages. It was normally connected directly to the positive high voltage battery terminal, and the other battery terminal was securely grounded. The use of bare electrical connections meant that users could be shocked if they touched the bare headphone connections while adjusting an uncomfortable headset. In 1958, John C. Koss, an audiophile and jazz musician from
Milwaukee Milwaukee ( ), officially the City of Milwaukee, is both the most populous and most densely populated city in the U.S. state of Wisconsin and the county seat of Milwaukee County. With a population of 577,222 at the 2020 census, Milwaukee i ...
, produced the first stereo headphones. Smaller earbud type earpieces, which plugged into the user's ear canal, were first developed for hearing aids. They became widely used with transistor radios, which commercially appeared in 1954 with the introduction of the
Regency TR-1 The Regency TR-1 was the first commercially manufactured transistor radio, introduced in 1954. Despite mediocre performance, about 150,000 units were sold, due to the novelty of its small size and portability. Previously, transistors had only bee ...
. The most popular audio device in history, the transistor radio changed listening habits, allowing people to listen to radio anywhere. The earbud uses either a moving iron driver or a piezoelectric crystal to produce sound. The 3.5 mm radio and phone connector, which is the most commonly used in portable application today, has been used at least since the Sony EFM-117J transistor radio, which was released in 1964. Its popularity was reinforced with its use on the Walkman portable tape player in 1979.


Applications

Headphones may be used with stationary CD and
DVD player A DVD player is a device that plays DVDs produced under both the DVD-Video and DVD-Audio technical standards, two different and incompatible standards. Some DVD players will also play audio CDs. DVD players are connected to a television to ...
s, home theater,
personal computer A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or te ...
s, or portable devices (e.g., digital audio player/ MP3 player,
mobile phone A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link whi ...
), as long as these devices are equipped with a headphone jack.
Cordless The term cordless is generally used to refer to electrical or electronic devices that are powered by a battery or battery pack and can operate without a power cord or cable attached to an electrical outlet to provide mains power, allowing greater ...
headphones are not connected to their source by a cable. Instead, they receive a
radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30  hertz (Hz) and 300  gigahertz (GHz). They are generated by an electronic device called a tr ...
or
infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...
signal encoded using a radio or infrared transmission link, such as FM,
Bluetooth Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is limi ...
or
Wi-Fi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio waves ...
. These are battery-powered receiver systems, of which the headphone is only a component. Cordless headphones are used with events such as a
Silent disco A silent disco or silent rave is an event where people dance to music listened to on wireless headphones. Rather than using a speaker system, music is broadcast via a radio transmitter with the signal being picked up by wireless headphone recei ...
or Silent Gig. In the professional audio sector, headphones are used in live situations by
disc jockey A disc jockey, more commonly abbreviated as DJ, is a person who plays recorded music for an audience. Types of DJs include radio DJs (who host programs on music radio stations), club DJs (who work at a nightclub or music festival), mobil ...
s with a DJ mixer, and sound engineers for monitoring signal sources. In radio studios, DJs use a pair of headphones when talking to the microphone while the speakers are turned off to eliminate acoustic feedback while monitoring their own voice. In studio recordings, musicians and singers use headphones to play or sing along to a backing track or band. In military applications, audio signals of many varieties are monitored using headphones. Wired headphones are attached to an audio source by a cable. The most common connectors are 6.35 mm (inch) and 3.5 mm phone connectors. The larger 6.35 mm connector is more common on fixed location home or professional equipment. The 3.5 mm connector remains the most widely used connector for portable application today. Adapters are available for converting between 6.35 mm and 3.5 mm devices. As active component, wireless headphones tend to be costlier due to the necessity for internal hardware such as a battery, a charging controller, a speaker driver, and a wireless transceiver, whereas wired headphones are a passive component, outsourcing speaker driving to the audio source. Some headphone cords are equipped with a serial potentiometer for volume control. Wired headphones may be equipped with a non-detachable cable or a detachable auxiliary male-to-male plug, as well as some with two ports to allow connecting another wired headphone in a
parallel circuit Two-terminal components and electrical networks can be connected in series or parallel. The resulting electrical network will have two terminals, and itself can participate in a series or parallel topology. Whether a two-terminal "object" is ...
, which splits the audio signal to share with another participant, but can also be used to hear audio from two inputs simultaneously. An external audio splitter can retrofit this ability.


Applications for audiometric testing

Various types of specially designed headphones or earphones are also used to evaluate the status of the auditory system in the field of audiology for establishing hearing thresholds, medically diagnosing
hearing loss Hearing loss is a partial or total inability to hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to acquire spoken l ...
, identifying other hearing related disease, and monitoring hearing status in occupational
hearing conservation program Hearing conservation programs are designed to prevent hearing loss due to noise. Hearing conservation programs require knowledge about risk factors such as noise and ototoxicity, hearing, hearing loss, protective measures to prevent hearing loss ...
s. Specific models of headphones have been adopted as the standard due to the ease of calibration and ability to compare results between testing facilities. Supra-aural style headphones are historically the most commonly used in audiology as they are the easiest to calibrate and were considered the standard for many years. Commonly used models are the Telephonics Dynamic Headphone (TDH) 39, TDH-49, and TDH-50. In-the-ear or insert style earphones are used more commonly today as they provide higher levels of interaural attenuation, introduce less variability when testing 6,000 and 8,000 Hz, and avoid testing issues resulting from collapsed ear canals. A commonly used model of insert earphone is the Etymotic Research ER-3A. Circum-aural earphones are also used to establish hearing thresholds in the extended high frequency range (8,000 Hz to 20,000 kHz). Along with Etymotic Research ER-2A insert earphones, the Sennheiser HDA300 and Koss HV/1A circum-aural earphones are the only models that have reference equivalent threshold sound pressure level values for the extended high frequency range as described by ANSI standards. Audiometers and headphones must be calibrated together. During the calibration process, the output signal from the audiometer to the headphones is measured with a sound level meter to ensure that the signal is accurate to the reading on the audiometer for sound pressure level and
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
. Calibration is done with the earphones in an acoustic coupler that is intended to mimic the transfer function of the outer ear. Because specific headphones are used in the initial audiometer calibration process, they cannot be replaced with any other set of headphones, even from the same make and model.


Electrical characteristics

Electrical characteristics of dynamic loudspeakers The chief electrical characteristic of a dynamic loudspeaker's driver is its electrical impedance as a function of frequency. It can be visualized by plotting it as a graph, called the impedance curve. Explanation The most common driver type i ...
may be readily applied to headphones, because most headphones are small dynamic loudspeakers.


Impedance

Headphones are available with high or low impedance (typically measured at 1 kHz). Low-impedance headphones are in the range 16 to 32 ohms and high-impedance headphones are about 100-600 ohms. As the impedance of a pair of headphones increases, more voltage (at a given current) is required to drive it, and the loudness of the headphones for a given voltage decreases. In recent years, impedance of newer headphones has generally decreased to accommodate lower voltages available on battery powered
CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", ) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSF ...
-based portable electronics. This has resulted in headphones that can be more efficiently driven by battery-powered electronics. Consequently, newer amplifiers are based on designs with relatively low output impedance. The impedance of headphones is of concern because of the output limitations of amplifiers. A modern pair of headphones is driven by an amplifier, with lower impedance headphones presenting a larger load. Amplifiers are not ideal; they also have some output impedance that limits the amount of power they can provide. To ensure an even frequency response, adequate damping factor, and undistorted sound, an amplifier should have an output impedance less than 1/8 that of the headphones it is driving (and ideally, as low as possible). If output impedance is large compared to the impedance of the headphones, significantly higher distortion is present. Therefore, lower impedance headphones tend to be louder and more efficient, but also demand a more capable amplifier. Higher impedance headphones are more tolerant of amplifier limitations, but produce less volume for a given output level. Historically, many headphones had relatively high impedance, often over 500 ohms so they could operate well with high-impedance
tube amplifiers A valve amplifier or tube amplifier is a type of electronic amplifier that uses vacuum tubes to increase the amplitude or power of a signal. Low to medium power valve amplifiers for frequencies below the microwaves were largely replaced by so ...
. In contrast, modern transistor amplifiers can have very low output impedance, enabling lower-impedance headphones. Unfortunately, this means that older audio amplifiers or stereos often produce poor-quality output on some modern, low-impedance headphones. In this case, an external
headphone amplifier A headphone amplifier is a low-powered audio amplifier designed particularly to drive headphones worn on or in the ears, instead of loudspeakers in speaker enclosures. Most commonly, headphone amplifiers are found embedded in electronic devices th ...
may be beneficial.


Sensitivity

Sensitivity is a measure of how effectively an earpiece converts an incoming electrical signal into an audible sound. It thus indicates how loud the headphones are for a given electrical drive level. It can be measured in decibels of sound pressure level per milli
watt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...
(dB (SPL)/mW) or decibels of sound pressure level per
volt The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827). Defin ...
(dB (SPL) / V). Unfortunately, both definitions are widely used, often interchangeably. As the output voltage (but not power) of a headphone amplifier is essentially constant for most common headphones, dB/mW is often more useful if converted into dB/V using
Ohm's law Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance, one arrives at the usual mathematical equa ...
: :\mathrm/\mathrm = \mathrm/\mathrm - 10 \cdot \log_ Once the sensitivity per volt is known, the maximum volume for a pair of headphones can be easily calculated from the maximum amplifier output voltage. For example, for a headphone with a sensitivity of 100 dB (SPL)/V, an amplifier with an output of 1 root mean square (RMS)
voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...
produces a maximum volume of 100 dB. Pairing high-sensitivity headphones with power amplifiers can produce dangerously high volumes and damage headphones. The maximum sound pressure level is a matter of preference, with some sources recommending no higher than 110 to 120 dB. In contrast, the American
Occupational Safety and Health Administration The Occupational Safety and Health Administration'' (OSHA ) is a large regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. Congress established the agen ...
recommends an average SPL of no more than 85 dB(A) to avoid long-term hearing loss, while the
European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are located primarily in Europe, Europe. The union has a total area of ...
standard EN 50332-1:2013 recommends that volumes above 85 dB(A) include a warning, with an absolute maximum volume (defined using 40–4,000 Hz noise) of no more than 100 dB to avoid accidental hearing damage. Using this standard, headphones with sensitivities of 90, 100 and 110 dB (SPL)/V should be driven by an amplifier capable of no more than 3.162, 1.0 and 0.3162 RMS volts at maximum volume setting, respectively to reduce the risk of hearing damage. The sensitivity of headphones is usually between about 80 and 125 dB/mW and usually measured at 1 kHz.


Specifications

Headphone size can affect the balance between fidelity and portability. Generally, headphone form factors can be divided into four separate categories: ''circumaural (over-ear)'', ''supra-aural (on-ear)'', ''earbud'' and ''in-ear''.


Connectivity


Wired

Headphones with soldered headphone jack cables.


Wireless

* Wireless on-ear headphones. Often have an inbuilt headphone jack. * Wireless over-ear headphones. Often have an inbuilt headphone jack. * Wireless earphones connected via a neckband.


True wireless

True wireless earbuds have no cord to keep each bud connected to each other. They rely on wireless technology such as
Bluetooth Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is limi ...
to transmit audio from a hardware device.


Ear adaption


Circumaural

Circumaural headphones (sometimes called full size headphones or over-ear headphones) have circular or ellipsoid earpads that encompass the ears. Because these headphones completely surround the ear, circumaural headphones can be designed to fully seal against the head to attenuate external noise. Because of their size, circumaural headphones can be heavy and there are some sets that weigh over . Ergonomic headband and earpad design is required to reduce discomfort resulting from weight. These are commonly used by drummers in recording.


Supra-aural

Supra-aural headphones or on-ear headphones have pads that press against the ears, rather than around them. They were commonly bundled with
personal stereo A personal stereo, or personal cassette player, is a portable audio player using an audiocassette player, battery power and in some cases an AM/FM radio. This allows the user to listen to music through headphones while walking, jogging or relaxin ...
s during the 1980s. This type of headphone generally tends to be smaller and lighter than circumaural headphones, resulting in less attenuation of outside noise. Supra-aural headphones can also lead to discomfort due to the pressure on the ear as compared to circumaural headphones that sit around the ear. Comfort may vary due to the earcup material.


Ear-fitting headphones


= Earphones

= Earphones are very small headphones that are fitted directly in the outer ear, facing but not inserted in the ear canal. Earphones are portable and convenient, but many people consider them uncomfortable. They provide hardly any acoustic isolation and leave room for ambient noise to seep in; users may turn up the volume dangerously high to compensate, at the risk of causing
hearing loss Hearing loss is a partial or total inability to hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to acquire spoken l ...
. On the other hand, they let the user be better aware of their surroundings. Since the early days of the transistor radio, earphones have commonly been bundled with personal music devices. They are sold at times with foam or rubber pads for comfort. (The use of the term ''earbuds'', which has been around since at least 1984, did not hit its peak until after 2001, with the success of Apple's MP3 player.)


= In-ear headphones

= In-ear headphones, also known as in-ear monitors (IEMs) or canalphones, are small headphones with similar portability to earbuds that are inserted in the ear canal itself. IEMs are higher-quality in-ear headphones and are used by
audio engineer An audio engineer (also known as a sound engineer or recording engineer) helps to produce a recording or a live performance, balancing and adjusting sound sources using equalization, dynamics processing and audio effects, mixing, reproduction ...
s and musicians as well as audiophiles. The outer shells of in-ear headphones are made up of a variety of materials, such as plastic,
aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
, ceramic and other metal alloys. Because in-ear headphones engage the ear canal, they can be prone to sliding out, and they block out much environmental noise. Lack of sound from the environment can be a problem when sound is a necessary cue for safety or other reasons, as when walking, driving, or riding near or in vehicular traffic. Some in-ear headphones utilize built-in microphones to allow some outside sound to be heard when desired. Generic or custom-fitting ear canal plugs are made from
silicone A silicone or polysiloxane is a polymer made up of siloxane (−R2Si−O−SiR2−, where R = organic group). They are typically colorless oils or rubber-like substances. Silicones are used in sealants, adhesives, lubricants, medicine, cookin ...
rubber, elastomer, or foam. Such plugs in lower-end devices may be interchangeable, which increases the risk of them falling off and getting lodged in the ear canal. Custom in-ear headphones use castings of the ear canal to create custom-molded plugs that provide added comfort and noise isolation. Some wireless earphones include a charging case.


Open- or closed-back

Both circumaural and supra-aural headphones can be further differentiated by the type of earcups:


Open-back

Open-back headphones have the back of the earcups open. This leaks more sound out of the headphone and also lets more ambient sounds into the headphone, but gives a more natural or speaker-like sound, due to including sounds from the environment.


Semi-open

Semi-open headphones, have a design that can be considered as a compromise between open-back headphones and closed-back headphones. Some believe the term "semi-open" is purely there for marketing purposes. There is no exact definition for the term semi-open headphone. Where the open-back approach has hardly any measure to block sound at the outer side of the diaphragm and the closed-back approach really has a closed chamber at the outer side of the diaphragm, a semi-open headphone can have a chamber to partially block sound while letting some sound through via openings or vents.


Closed-back

Closed-back (or sealed) styles have the back of the earcups closed. They usually block some of the ambient noise. Closed-back headphones usually can produce stronger low frequencies than open-back headphones.


Headset

A headset is a headphone combined with a
microphone A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and publ ...
. Headsets provide the equivalent functionality of a telephone handset with hands-free operation. Among applications for headsets, besides telephone use, are aviation, theatre or television studio intercom systems, and console or PC gaming. Headsets are made with either a single-earpiece (mono) or a double-earpiece (mono to both ears or stereo). The microphone arm of headsets is either an external microphone type where the microphone is held in front of the user's mouth, or a voicetube type where the microphone is housed in the earpiece and speech reaches it by means of a hollow tube.


Telephone headsets

Telephone headsets connect to a
fixed-line A landline (land line, land-line, main line, home phone, fixed-line, and wireline) is a telephone connection that uses metal wires or optical fiber telephone line for transmission, as distinguished from a mobile cellular network, which uses ...
telephone system. A telephone headset functions by replacing the handset of a telephone. Headsets for standard corded telephones are fitted with a standard 4P4C commonly called an RJ-9 connector. Headsets are also available with 2.5 mm jack sockets for many DECT phones and other applications. Cordless
bluetooth Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is limi ...
headsets are available, and often used with mobile telephones. Headsets are widely used for telephone-intensive jobs, in particular by
call centre A call centre ( Commonwealth spelling) or call center (American spelling; see spelling differences) is a managed capability that can be centralised or remote that is used for receiving or transmitting a large volume of enquiries by telephone ...
workers. They are also used by anyone wishing to hold telephone conversations with both hands free. For older models of telephones, the headset microphone impedance is different from that of the original handset, requiring a telephone amplifier for 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 switching between headset and handset. Telephone amplifiers are powered by batteries or AC adaptors.


Communication headsets

Communication headsets are used for two-way communication and typically consist of a headphone and attached microphone. Such headsets are used in a variety of professions as aviation, military, sports, music, and many service-oriented sectors. They come in all shapes and sizes, depending on use, required noise attenuation, and fidelity of communication needed.


Ambient noise reduction

Unwanted sound from the environment can be reduced by excluding sound from the ear by passive noise isolation, or, often in conjunction with isolation, by active noise cancellation. Passive noise isolation is essentially using the body of the earphone, either over or in the ear, as a passive earplug that simply blocks out sound. The headphone types that provide most attenuation are in-ear canal headphones and closed-back headphones, both circumaural and supra aural. Open-back and earbud headphones provide some passive noise isolation, but much less than the others. Typical closed-back headphones block 8 to 12 dB, and in-ears anywhere from 10 to 15 dB. Some models have been specifically designed for drummers to facilitate the drummer monitoring the recorded sound while reducing sound directly from the drums as much as possible. Such headphones claim to reduce ambient noise by around 25 dB. Active noise-cancelling headphones use a microphone, amplifier, and speaker to pick up, amplify, and play ambient noise in phase-reversed form; this to some extent cancels out unwanted noise from the environment without affecting the desired sound source, which is not picked up and reversed by the microphone. They require a power source, usually a battery, to drive their circuitry. Active noise cancelling headphones can attenuate ambient noise by 20 dB or more, but the active circuitry is mainly effective on constant sounds and at lower frequencies, rather than sharp sounds and voices. Some noise cancelling headphones are designed mainly to reduce low-frequency engine and travel noise in aircraft, trains, and automobiles, and are less effective in environments with other types of noise.


Transducer technology

Headphones use various types of transducer to convert electrical signals to sound.


Moving-coil

The moving coil driver, more commonly referred to as a "dynamic" driver is the most common type used in headphones. It consists of a stationary
magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nicke ...
element affixed to the frame of the headphone, which sets up a static magnetic field. The magnet in headphones is typically composed of ferrite or
neodymium Neodymium is a chemical element with the symbol Nd and atomic number 60. It is the fourth member of the lanthanide series and is considered to be one of the rare-earth metals. It is a hard, slightly malleable, silvery metal that quickly tarn ...
. A voice coil, a light coil of wire, is suspended in the magnetic field of the magnet, attached to a diaphragm, typically fabricated from lightweight, high-stiffness-to-mass-ratio cellulose, polymer, carbon material, paper or the like. When the varying current of an audio signal is passed through the coil, it creates a varying magnetic field that reacts against the static magnetic field, exerting a varying force on the coil causing it and the attached diaphragm to vibrate. The vibrating diaphragm pushes on the air to produce
sound wave In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...
s.


Electrostatic

Electrostatic drivers consist of a thin, electrically charged diaphragm, typically a coated PET film membrane, 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 diaphragm is drawn towards one of the plates. Air is forced through the perforations; combined with a continuously changing electrical signal driving the membrane, a sound wave is generated. Electrostatic headphones are usually more expensive than moving-coil ones, and are comparatively uncommon. In addition, a special amplifier is required to amplify the signal to deflect the membrane, which often requires electrical potentials in the range of 100 to 1,000 volts. Due to the extremely thin and light diaphragm membrane, often only a few micrometers thick, and the complete absence of moving metalwork, the frequency response of electrostatic headphones usually extends well above the audible limit of approximately 20 kHz. The high-frequency response means that the low-midband distortion level is maintained to the top of the audible frequency band, which is generally not the case with moving coil drivers. Also, the frequency response peakiness regularly seen in the high-frequency region with moving coil drivers is absent. Well-designed electrostatic headphones can produce significantly better sound quality than other types. Electrostatic headphones require a voltage source generating 100 V to over 1 kV, and are on the user's head. Since the invention of insulators, there is no actual danger. They do not need to deliver significant
electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The movi ...
, which further limits the electrical hazard to the wearer in case of fault.


Electret

An electret driver functions along the same electromechanical means as an electrostatic driver. However the electret driver has a permanent charge built into it, whereas electrostatics have the charge applied to the driver by an external generator. Electret and electrostatic headphones are relatively uncommon. Original electrets were also typically cheaper and lower in technical capability and fidelity than electrostatics. Patent applications from 2009 to 2013 have been approved that show by using different materials, i.e. a "Fluorinated cyclic olefin electret film", Frequency response chart readings can reach 50 kHz at 100db. When these new improved electrets are combined with a traditional dome headphone driver, headphones can be produced that are recognised by the Japan Audio Society as worthy of joining the Hi Res Audio program. US patents 8,559,660 B2. 7,732,547 B2.7,879,446 B2.7,498,699 B2.


Planar magnetic

Planar magnetic (also known as orthodynamic) headphones use similar technology to electrostatic headphones, with some fundamental differences. They operate similarly to planar magnetic loudspeakers. A planar magnetic driver consists of a relatively large membrane that contains an embedded wire pattern. This membrane is suspended between two sets of permanent, oppositely aligned, magnets. A current passed through the wires embedded in the membrane produces a magnetic field that reacts with the field of the permanent magnets to induce movement in the membrane, which produces sound.


Balanced armature

A balanced armature is a sound transducer design primarily intended to increase the electrical efficiency of the element by eliminating the stress on the diaphragm characteristic of many other magnetic transducer systems. As shown schematically in the left diagram, it consists of a moving magnetic armature that is pivoted so it can move in the field of the permanent magnet. When precisely centered in the magnetic field there is no net force on the armature, hence the term 'balanced'. As illustrated in the right diagram, when there is
electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The movi ...
through the coil, it magnetizes the armature one way or the other, causing it to rotate slightly one way or the other about the pivot thus moving the
diaphragm Diaphragm may refer to: Anatomy * Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen * Pelvic diaphragm or pelvic floor, a pelvic structure * Urogenital diaphragm or triangular ligament, a pelvic structure Other * Diap ...
to make
sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by ...
. The design is not mechanically stable; a slight imbalance makes the armature stick to one pole of the magnet. A fairly stiff restoring force is required to hold the armature in the 'balance' position. Although this reduces its efficiency, this design can still produce more sound from less power than any other. Popularized in the 1920s as Baldwin Mica Diaphragm radio headphones, balanced armature transducers were refined during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
for use in military
sound powered telephone A sound-powered telephone is a communication device that allows users to talk to each other with the use of a handset, similar to a conventional telephone, but without the use of external power. This technology has been used since at least 194 ...
s. Some of these achieved astonishing electro-acoustic conversion efficiencies, in the range of 20% to 40%, for narrow bandwidth voice signals. Today they are typically used only in in-ear headphones and hearing aids, where their high efficiency and diminutive size is a major advantage. They generally are limited at the extremes of the hearing spectrum (e.g. below 20 Hz and above 16 kHz) and require a better seal than other types of drivers to deliver their full potential. Higher-end models may employ multiple armature drivers, dividing the frequency ranges between them using a passive crossover network. A few combine an armature driver with a small moving-coil driver for increased bass output. The earliest loudspeakers for radio receivers used balanced armature drivers for their cones.


Thermoacoustic technology

The thermoacoustic effect generates sound from the audio frequency Joule heating of the conductor, an effect that is not magnetic and does not vibrate the speaker. In 2013 a carbon nanotube thin-yarn earphone based on the thermoacoustic mechanism was demonstrated by a research group in Tsinghua University. The as-produced CNT thin yarn earphone has a working element called CNT thin yarn thermoacoustic chip. Such a chip is composed of a layer of CNT thin yarn array supported by the silicon wafer, and periodic grooves with certain depth are made on the wafer by micro-fabrication methods to suppress the heat leakage from the CNT yarn to the substrate.


Other transducer technologies

Transducer technologies employed much less commonly for headphones include the Heil Air Motion Transformer (AMT); Piezoelectric film; Ribbon planar magnetic; Magnetostriction and Plasma or Ionic. The first Heil AMT headphone was marketed by ESS Laboratories and was essentially an ESS AMT tweeter from one of the company's speakers being driven at full range. Since the turn of the century, only Precide of Switzerland have manufactured an AMT headphone. Piezoelectric film headphones were first developed by Pioneer, their two models used a flat sheet of film that limited the maximum volume of air movement. Currently, TakeT produces a piezoelectric film headphone shaped similarly to an AMT transducer but, which like the Precide driver, has a variation in the size of transducer folds over the diaphragm. It additionally incorporates a two way design by its inclusion of a dedicated tweeter/supertweeter panel. The folded shape of a diaphragm allows a transducer with a larger surface area to fit within smaller space constraints. This increases the total volume of air that can be moved on each excursion of the transducer given that radiating area. Due to the small volume of air in a headphone, the plasma or ionic transducer can become a full range driver although the high temperatures and voltages of these types makes them very rare with only the Plasmasonic being commercial. Magnetostriction headphones, sometimes sold under the label ''Bonephones'', work by vibrating against the side of head, transmitting sound via bone conduction. This is particularly helpful in situations where the ears must be unobstructed, or for people who are deaf for reasons that don't affect the nervous apparatus of hearing. Magnetostriction headphones though, are limited in their fidelity compared to conventional headphones that rely on the normal workings of the ear. Additionally, in the mid 1980s, a French company called Audio Reference tried to market the Plasmasonic plasma headphone invented by Henri Bondar. There are no known functioning examples left. Due to the small volume of air in a headphone, the plasma or ionic transducer can become a full range driver although the high temperatures and voltages needed makes them very rare.


Benefits and limitations

Headphones can prevent other people from hearing the sound, either for privacy or to prevent disturbing others, as in listening in a public
library A library is a collection of materials, books or media that are accessible for use and not just for display purposes. A library provides physical (hard copies) or digital access (soft copies) materials, and may be a physical location or a vi ...
. They can also provide a level of sound fidelity greater than loudspeakers of similar cost. Part of their ability to do so comes from the lack of any need to perform room correction treatments with headphones. High-quality headphones can have an extremely flat low-frequency response down to 20 Hz within 3 dB. While a loudspeaker must use a relatively large (often 15" or 18") speaker driver to reproduce low frequencies, headphones can accurately reproduce bass and sub-bass frequencies with speaker drivers only 40-50 millimeters wide (or much smaller, as is the case with in-ear monitor headphones). Headphones' impressive low-frequency performance is possible because they are so much closer to the ear that they only need to move relatively small volumes of air. Marketed claims such as 'frequency response 4 Hz to 20 kHz' are usually overstatements; the product's response at frequencies lower than 20 Hz is typically very small. Headphones are also useful for
video game Video games, also known as computer games, are electronic games that involves interaction with a user interface or input device such as a joystick, controller, keyboard, or motion sensing device to generate visual feedback. This feedba ...
s that use 3D positional audio processing algorithms, as they allow players to better judge the position of an off-screen sound source (such as the footsteps of an opponent or their gunfire). Although modern headphones have been particularly widely sold and used for listening to stereo recordings since the release of the Walkman, there is subjective debate regarding the nature of their reproduction of stereo sound. Stereo recordings represent the position of horizontal depth cues (stereo separation) via volume and phase differences of the sound in question between the two channels. When the sounds from two speakers mix, they create the phase difference the brain uses to locate direction. Through most headphones, because the right and left channels do not combine in this manner, the illusion of the phantom center can be perceived as lost. Hard panned sounds are also heard only in one ear rather than from one side. Binaural recordings use a different microphone technique to encode direction directly as phase, with very little amplitude difference below 2 kHz, often using a dummy head. They can produce a surprisingly lifelike spatial impression through headphones. Commercial recordings almost always use stereo recording, rather than binaural, because loudspeaker listening is more common than headphone listening. It is possible to change the spatial effects of stereo sound on headphones, to better approximate the presentation of speaker reproduction, by using frequency-dependent cross-feed between the channels. Headsets can have ergonomic benefits over traditional telephone handsets. They allow call center agents to maintain better posture without needing to hand-hold a handset or tilt their head sideways to cradle it.


Health and safety


Dangers and risks

Using headphones at a sufficiently high
volume Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). ...
level may cause temporary or permanent hearing impairment or
deafness Deafness has varying definitions in cultural and medical contexts. In medical contexts, the meaning of deafness is hearing loss that precludes a person from understanding spoken language, an audiological condition. In this context it is written ...
. The headphone volume often has to compete with the background noise, especially in loud places such as subway stations, aircraft, and large crowds. Extended periods of exposure to high sound pressure levels created by headphones at high volume settings may be damaging to hearing; Nearly 50% of teenagers and young adults (12 to 35 years old) in middle and high income countries listen to unsafe levels of sound on their personal audio devices and smartphones. However, one hearing expert found in 2012 (before the worldwide adoption of smartphones as the main personal listening devices) that "fewer than 5% of users select volume levels and listen frequently enough to risk hearing loss." The International Telecommunication Union recently published "Guidelines for safe listening devices/systems" recommended that sound exposure not exceed 80 decibels, A-weighted dB(A) for a maximum of 40 hours per week. The
European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are located primarily in Europe, Europe. The union has a total area of ...
have also set a similar limit for users of personal listening devices (80 dB(A) for no more than 40 hours per week) and for each additional increase of 3-dB in sound exposure, the duration should be cut in half (83 dB(A) for no more than 20 hours, 86 dB(A) for 10 hours per week, 89 dB(A) for 5 hours per week and so on. Most major manufactures of smartphones now include some safety or volume limiting features and warning messaging in their devices. though such practices have received mixed response from some segments of the buying who favor the personal choice of setting their own volume levels. The usual way of limiting sound volume on devices driving headphones is by limiting output power. This has the additional undesirable effect of being dependent of the efficiency of the headphones; a device producing the maximum allowed power may not produce adequate volume when paired with low-efficiency, high-impedance equipment, while the same amount of power can reach dangerous levels with very efficient earphones. Some studies have found that people are more likely to raise volumes to unsafe levels while performing strenuous exercise. A Finnish study recommended that exercisers should set their headphone volumes to half of their normal loudness and only use them for half an hour. Other than hearing risk, there is a general danger that listening to loud music in headphones can distract the listener and lead to injury and accidents. Noise-cancelling headphones add extra risk. Several countries and states have made it illegal to wear headphones while driving or cycling. There have also been numerous reports of contact dermatitis due to exposure to in-ear headphones such as Apple AirPods. The contact dermatitis would be caused by in-ear headphones that contain gold, rubber, dyes, acrylates, or methacrylates. However, there have been no studies done to prove that exposure to in-ear headphones will cause contact dermatitis, rather that there is a correlation between in-ear headphone use and contact dermatitis cases.


Occupational health and safety

Hearing risk from headphones' use also applies to workers who must wear electronic or communication headsets as part of their daily job (i.e., pilots, call center and dispatch operators, sound engineers , firefighters, etc.) and hearing damage depends on the exposure time. The National Institute for Occupational Safety and Health ( NIOSH) recommends sound exposure not exceed 85 dB(A) over 8 hour work day as a time-weighted average. NIOSH uses the 3-dB exchange rate often referred to as "time-intensity tradeoff" which means if sound exposure level is increased by 3 decibels, the duration of exposure should be cut in half. NIOSH published several documents targeted at protecting the hearing of workers who must wear communication headsets such as call center operators, firefighters, and musicians and sound engineers.


See also

* Bone conduction * Digital audio player *
Earmuffs Earmuffs are clothing accessories or personal protective equipment designed to cover a person's ears for hearing protection or warmth. They consist of a thermoplastic or metal head-band that fits over the top or back of the head, and a cushi ...
* Earpad *
Headphone amplifier A headphone amplifier is a low-powered audio amplifier designed particularly to drive headphones worn on or in the ears, instead of loudspeakers in speaker enclosures. Most commonly, headphone amplifiers are found embedded in electronic devices th ...
* In-ear monitor *
Loudspeaker A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or ...
* Noise-cancelling headphones


References


External links

* * {{Authority control
Phones A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into ele ...
Audio engineering Consumer electronics Loudspeakers Transducers Audiovisual introductions in 1910 Audiology