User:Mcfarland123/sandbox

Headphones (or head-phones in the early days of telephony and radio) traditionally refer to 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 to a corresponding sound. Headphones let a single user listen to an audio source privately, in contrast to a loudspeaker, which emits sound into the open air for anyone nearby to hear. Headphones are also known as earspeakers, earphones^[1] or, colloquially, cans.^[2] 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^[1] 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, a headset is a combination of headphone and microphone. Headphones connect to a signal source such as an audio amplifier, radio, CD player, portable media player, mobile phone, video game console, or electronic musical instrument, either directly using a cord, or using wireless technology such as Bluetooth, DECT or FM radio. 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.^[3]

Headphones are made in 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 connectivity to transmit the audio signal by radio waves from source devices like cellphones and digital players.^[4] Due to the spread of wireless devices in recent years headphones are increasingly used by people in public places such as sidewalks, grocery stores, and public transit. Headphones are also used by people in various professional contexts, such as audio engineers mixing sound for live concerts or sound recordings 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. Headphones that may also be referred to as earphones are a device that help us get the audio of a game, movie or any video or audio recording. The headphones were actually invented by Nathaniel Baldwin in 1910. In the past times (before Nathaniel’s invention) they didn’t have such a large scope of use as they have now. In the past times they were used as amplifiers for radio and telephones. But the history of modern headphones starts with the invention of Baldwin. It is to be noted here that the headphones have existed from 1880’s. In 1959 came the electrostatic headphones, the SR-1’s, showed in Tokyo. And in 1968, Koss again gave a move to his talents and produced ESP-6, the first electrostatic headphone made by U.S. These latest headphones were way more lighter than the traditional ones, e.g. 10 pounds. They weighed around 2 pounds. However, the invention of Walkman brought the most favorable change in the market of headphones as well as in its variety. Sony Walkman headphones were the smallest of all the headphones ever produced before. And they stood as an inspiration for all the headphones that would be produced later. In the ground of technology headphones have hit the shelves. They are paired with almost everything. For example, Computers, Laptops, Mobile Phones, Tablets, MP3’s, MP4’s, LCD’s and many more devices carry with them a need or an expectation for the connection of headphones with them.

History

Brandes radio headphones, circa 1920 Headphones originated from the telephone receiver earpiece, and were the only way to listen to electrical audio signals before amplifiers were developed. The first truly successful set was developed in 1910 by Nathaniel Baldwin, who made them by hand in his kitchen and sold them to the United States Navy.^[5][6]

These early headphones used moving iron drivers,^[7] 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 and telephone work had an impedance of 75 ohms. Those used with early wireless radio had more turns of finer wire to increase sensitivity. Impedance of 1000 to 2000 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'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, produced the first stereo headphones.^[8][7] Previously, headphones were used only by the US navy, telephone and radio operators, and individuals in similar industries.^[7]

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 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.^[9][10] Its popularity was reinforced with its use on the Walkman portable tape player in 1979. Now a days we see a range of headphones: Closed-back headphones, open-back headphones, on-ear headphones, over-ear headphones, in-ear headphones and earbuds etc. all are just different forms of the headphones. We were still in the 80’s and 90’s when we witnessed some modifications and innovations in the already much advanced headphones e.g. earbuds, neckband headphones and noise canceling headphones. It was Dr. Amar Bose who invented noise canceling headphones, intentionally created for the pilots to escape deafening noise and distractions in the cockpits. The last but not at all least, in fact the most craziest and bold step was taken by Dr. Dre and his business partner Jimmy Iovine in this ground.

Applications

Headphones may be used with stationary CD and DVD players, home theater, personal computers, or portable devices (e.g., digital audio player/MP3 player, mobile phone). Cordless headphones are not connected to their source by a cable. Instead, they receive a radio or infrared signal encoded using a radio or infrared transmission link, such as FM, Bluetooth or Wi-Fi. These are powered receiver systems, of which the headphone is only a component. Cordless headphones are used with events such as a Silent disco or Silent Gig. Sennheiser HD 555 headphones, used in audio production environments (2007)

In the professional audio sector, headphones are used in live situations by disc jockeys 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 (¼″) 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.

Electrical characteristics

Electrical characteristics of dynamic loudspeakers 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-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.^[11] 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. 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 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 milliwatt (dB (SPL)/mW) or decibels of sound pressure level per volt (dB (SPL) / V).^[12] 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:

Alternatively, online calculators can be used.^[13] 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 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 recommends an average SPL of no more than 85 dB(A) to avoid long-term hearing loss, while the European Union standard EN 50332-1:2013 recommends that volumes above 85 dB(A) include a warning, with an absolute maximum volume (defined using 40–4000 Hz noise) of no more than 100 dB to avoid accidental hearing damage.^[14] 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.^[15]

Types

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.

Circumaural

Circumaural headphones have large pads that surround the outer ear. 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 500 grams (1 lb). Ergonomic headband and earpad design is required to reduce discomfort resulting from weight. These are commonly used by drummers in recording.

Supra-aural

A pair of supra-aural (on-ear) headphones Supra-aural headphones or on-ear headphones have pads that press against 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 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.

Open or closed back

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

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.

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.

Semi-open headphones, have a design that can be considered as a compromise between open-back headphones and closed-back headphones. Some^[who?] 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.

Ear-fitting headphones

Earphones

Earbuds/earphones sit in the outer ear

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.^[16] 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.^[16][17] 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 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.^[18])

In-ear headphones

Main article: In-ear monitor In-ear monitors extend into the ear canal, providing isolation from outside noise. 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 canalitself. IEMs are higher-quality in-ear headphones and are used by audio engineers 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, 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.^[19]

Generic or custom-fitting ear canal plugs are made from silicone rubber, elastomer, or foam. Custom in-ear headphones use castings of the ear canal to create custom-molded plugs that provide added comfort and noise isolation.^[16]

Mixed fitting pivoting earphones

NeckTec IEMs with rotating Z-shaped shaft for constant wear in 1of2 positions: "comfort" for quiet indoors and "quality" for noise insulation & powerful sound. This type combines advantages of earbuds and in-ear headphones – depending on the environment and requirements of the user, they provide passive noise reduction for quality mode (conversation or active music listening) or they give control over the sound environment around user in comfort mode (stand by or background voice/music listening).^{[citation needed]}

Headset

Main article: Headset (audio) 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. 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.

There are two main components in a set of headphones: two mini loudspeakers and a housing for these speakers. The tiny loudspeakers are made using metal compounds together with paper or plastic. Headphone housings, depending on the design, are manufactured from a combination of rubber, plastic and foam and allow the headphones to sit comfortably on one’s ear.

Headphones have two transducers that enable the conversion of electrical energy into sound energy, which our ears perceive as music or spoken word. Transducers are essentially devices that can convert different types of energy. At the end of the day, a set of headphones is exactly like a regular circuit because there is a conductor that takes current from a source of power and provides it to a load (the transducer).

Each set of headphones consists of two wires. One wire connects the source of power to the transducer, while the other wire (the ground) will complete its circuit. These two wires are always insulated (normally with a protective plastic coating) that looks pleasing to the eye.

Since headphones are miniature versions of loudspeakers, they work on the same principles of sound reproduction, i.e. by converting electrical signals into sound waves. The source of sound (e.g.. music) will send a signal as an alternating current via a cable to the headphone’s drivers, which are tiny speakers within the headphones. This signal will then be sent through to the voice coil which is situated in the driver which will create a magnetic field. A fixed magnet surrounds the voice coil and the alternating current within it will repel and attract it from the magnet.

Telephone headsets

Sony Ericsson Cordless bluetooth headset Telephone headsets connect to a fixed-line 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 headsets are available, and often used with mobile telephones. Headsets are widely used for telephone-intensive jobs, in particular by call centre 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 headset used by aviators 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

In-ears are among those good for noise isolation 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

A typical moving-coil headphone transducer 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 magnetelement 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. 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 waves.

Electrostatic

Electrostatic loudspeaker diagram 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 1000 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.^{[citation needed]}

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's no actual danger. They do not need to deliver significant electric current, 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 2009-2013 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

Balanced armature transducer with armature balanced and exerting no force on diaphragm 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 first 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 second diagram, when there is electric current 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 to make sound. A custom in-ear monitor which uses 8 balanced armatures in a triple crossover configuration (4 low/2 mid/2 high). Headphone designs often use multiple balanced armatures to provide a higher fidelity sound. 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^{[clarification needed]}. Popularized in the 1920s as Baldwin Mica Diaphragm radio headphones, balanced armature transducers were refined during World War II for use in military sound powered telephones. 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.^[20] 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.^[21]

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.^[22]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.^{[citation needed]}

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-ionisation. 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.

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 early 1990s, a French company called Plasmasonics tried to market a plasma-ionisation headphone. There are no known functioning examples left.

Benefits and limitations

Two Sony MDR-V6 headphones, one folded for travel

Headphones can prevent other people from hearing the sound, either for privacy or to prevent disturbing others, as in listening in a public library. 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.^[23] Headphones are also useful for video games 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.^[24]

Health and safety

See also: Automatic volume limiter

Dangers and risks

Product testing - headphones in an anechoic chamber Using headphones at a sufficiently high volume level may cause temporary or permanent hearing impairment or deafness. 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;^[25][26] 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.^[27] 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."^[28] 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.^[29] The European Union 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.^[30][31] 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.^[32] A Finnish study^[33] 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.^[34]

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.^[35] 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,^[36] firefighters,^[37] and musicians and sound engineers.^[38]

References

Week 2: Evaluate a Wikipedia article

Article Evaluation

I will be evaluating the below article

Motorized scooter

Everything in this article is relevant to the article topic, Nothing distracted me about this article but the fact that this article wasn’t that much detailed so it wasn’t much info about it. It could be improved by being a longer article. The article is very neutral, and it doesn’t seem biased at all. The view points are underrepresented in this article. I checked the citations and the links do work and they are accurate. The sources do support the claims.

Reflective Essay

I felt that adding my value to the article gave it a little more significance because I think that what I had to add also gives the article itself more value because of the extra added information being put into it. The way my article compares to an earlier version is that there is more information and changed a few things to make it easier to understand certain concepts. No, I got my peer review from Wiki not an actual classmate, which gave help me get a better perspective from a non-classroom mindset on the article and how it can be more appealing when reading and talking to the audience. They informed me to make a few editing changes as well do more research do make sure that the information being inputted was solid.

I did receive feedback from other Wiki editors, some of it was good and some of it was bad, but not in a way that it bothered me but, in a way, to help me make better revisions as well, when I do future articles. I handled the feedback pretty well as I am all for self-criticism it is one of those things that helps me grow because someone else can see what I cannot from a different view or perspective. Also, I have learned that not all feedback is personal but to help give insight to things and open my awareness. What I've learned to contributing to Wikipedia is that it actually helps and makes a difference when it comes to providing information about topics people are interested in.

Not only that but I can say that I put my energy towards something small but meaningful and beneficial to someone else's learning. This assignment was different because I had to think outside the box and look at the project from a different angle then I am normally used to doing things. It can be helped to improve the public's understanding on the field/topic because Wiki is usually one of the first sources that come up when looking for information. So, that helps naturally bring people's awareness more to reading the information at hand. This is important because it helps people get information faster without having to look in tons of places and they also know the information can be coming from a reliable source from a person who knows what they are talking about.

assignment 9 completed[edit]

i saw some feed back from wikipedia someone and i think it was useful it made me go back and make sure my info was more accurate. they actually took it down and told me that it sounded like i was freely talking etc so it made me go back and do more research and revise things and make it a little bit more accurate

Ryan Whritenour peer review[edit]

I liked Ryan's article about the electric switch board this is a important part of technology, and i appreciate it greatly I'm still having issues choosing mine but i will have that fixed soon, but great article and keep up the great work. This article is very relevant to technology and the article is not to long so its a lot of info that ryan can add to it, to make it a more stronger article and hopefully wiki will keep his contributions. this article has structure and it is well put together in order from top to bottom it makes logical sense. there is only one source though. so way more info can be added to this article. Mcfarland123 (talk) 22:49, 11 July 2019 (UTC) bryan benn

July 2019[edit]

Hello, I'm GorillaWarfare. I wanted to let you know that I reverted one of your recent contributions —specifically this edit to Headphones— because it did not appear constructive. If you would like to experiment, please use the sandbox. If you have any questions, you can ask for assistance at the Help desk. Thanks. GorillaWarfare (talk) 03:44, 7 July 2019 (UTC)

assignment 5[edit]

“A Look at Headphones through Time.” Earphone Solutions, www.earphonesolutions.com/headphones-through-time.

Quirky. “Great Inventions: History and Evolution of the Headphone.” Quirky, shop.quirky.com/blogs/news/great-inventions-history-of-headphone.

Ssense. “A History of Headphone Design.” Ssense, 20 Feb. 2017, www.ssense.com/en-us/editorial/culture/a-history-of-headphone-design.

Stamp, Jimmy. “A Partial History of Headphones.” Smithsonian.com, Smithsonian Institution, 19 Mar. 2013, www.smithsonianmag.com/arts-culture/a-partial-history-of-headphones-4693742/.

“The History of Headphones.” Visual.ly, visual.ly/community/infographic/technology/history-headphones.

“The History of Headphones.” Cool Material, 5 Sept. 2017, coolmaterial.com/roundup/history-of-headphones/.

“What Are Headphones?” Computer Hope, 30 June 2019, www.computerhope.com/jargon/h/headphon.htm.

Assignment 6[edit]

These initial headphones of 1880’s had a single piece that was to be set over the shoulder. It had a weight of 10 pounds. While the design of headphones introduced by Baldwin is much similar to what we see now a days. Nathaniel got success for his invention, he got an order to make headphones for the U.S Navy. It was the first headphone to have pieces for both ears. With time headphones have gone through tremendous development. And these later developments of headphones were made by Beyer dynamic, and AKG, with the production of DT-48 dynamic headphones in 1937 and K120 in 1949 respectively.

Both achievements were enough to surprise the people of the time, pushing one’s thinking beyond the limits. After that in 1958 came the stereo headphones marking again a distinction from the former. This invention was made by a jazz musician and audiophile John C. Koss. In 1959 came the electrostatic headphones, the SR-1’s, showed in Tokyo. And in 1968, Koss again gave a move to his talents and produced ESP-6, the first electrostatic headphone made by U.S. These latest headphones were way more lighter than the traditional ones, e.g. 10 pounds.

They weighed around 2 pounds. However, the invention of Walkman brought the most favorable change in the market of headphones as well as in its variety. Sony Walkman headphones were the smallest of all the headphones ever produced before. And they stood as an inspiration for all the headphones that would be produced later. In the ground of technology headphones have hit the shelves. They are paired with almost everything. For example, Computers, Laptops, Mobile Phones, Tablets, MP3’s, MP4’s, LCD’s and many more devices carry with them a need or an expectation for the connection of headphones with them.

Now a days we see a range of headphones: Closed-back headphones, open-back headphones, on-ear headphones, over-ear headphones, in-ear headphones and earbuds etc. all are just different forms of the headphones.

We were still in the 80’s and 90’s when we witnessed some modifications and innovations in the already much advanced headphones e.g. earbuds, neckband headphones and noise canceling headphones. It was Dr. Amar Bose who invented noise canceling headphones, intentionally created for the pilots to escape deafening noise and distractions in the cockpits. The last but not at all least, in fact the most craziest and bold step was taken by Dr. Dre and his business partner Jimmy Iovine in this ground. They, using the name of their brand ‘Beats by Dre’, introduced Beats headphones. Like all other products of this brand these headphones were also over-priced. The price of these products was not based on the quality of these products but more on the name of this brand. “Lil’ Wayne even purchased a $1 million dollar pair of diamond studded Beats headphones. “But this also doesn’t mean that these headphones are nothing.