It covers everything from audio for wireless headphones and speakers, pairing gaming controllers and keyboards, tethering internet connections, and even occasionally transferring files over the air. At the time, it was designed to replace RS-232 telecommunication cables, a much older standard conceived in 1960, by using short-range UHF radio waves between 2.4 and 2.485 GHz.
Although this occupies very similar frequencies to Wi-Fi, Bluetooth has always been designed as a much shorter range and lower power alternative.
In 1988 the Bluetooth Special Interest Group (SIG) was formed, which to this day publishes and promotes the standard and its subsequent revisions.
Bluetooth SIG initially only included Ericsson, IBM, Intel, Nokia, and Toshiba, but reached 4,000 members by the end of its first year. The Bluetooth 1.0 specification also officially launched that year, leading to the release of the first Bluetooth-equipped chipsets, dongles, mice, wireless PC cards, and mobile phones in 2000.
The first Bluetooth mobile phone was the Sony Ericsson T36, but it was the revised T39 model which actually made it to store shelves in 2001. It offered customers a 101 x 54 Monochrome LCD display, tri-band GSM connectivity, WAP internet, and enough memory to store up to 1,000 contacts.
The RS-232 standard was widely used as a computer serial port, catering to internet modems, printers, mice, data storage, and a host of other peripherals.
As its proposed replacement, Bluetooth was designed as a flexible packet-based protocol with a wide selection of profiles to suit these applications and more.
The 1.0 specification offered peak data speeds of just 721 kbps and connections couldn’t reach much farther than 10 meters. Once you factored in real-world performance, longer-range connection quality, and the rather hefty header packets, the actual data rate available to applications was notably slower.
The standard originally offered profiles for wireless voice and headsets, dial-up networking, fax, and file transfers. It’s the cornerstone of mobile and console gaming controllers, a key component in modern smart home equipment, fitness trackers, and mesh networks that are increasingly useful for industrial applications. Probably the most common use for Bluetooth in modern products is audio, yet the original standard was never designed for anything close to full bandwidth music. 721 Kbps is enough for a good voice compression codec, even once you discount the header overheads and diminishing real-world speeds at distance, but such limited bandwidth couldn’t hope to cater to anything close Hi-Res audio today or even CD quality at the time.
Bluetooth was originally conceived with wireless voice calls in mind but not high-quality music streaming. The Bluetooth specification has undergone numerous revisions since 1999 to improve the standard’s data speeds and connection quality, feature set, and to help accommodate all these new use cases and markets.
Most recently, Bluetooth SIG has been focusing on audio, mesh networking, lower energy profiles, and a longer range for IoT. Bluetooth 5.0 introduced Slot Available Masking to reduce interference with 4G LTE by scheduling data transmissions.
The table below shows when these major features were introduced, and how typical use cases for speed and range have evolved over time. Rather than evolving in a single path, the standard has split into Low Energy and Classic segments since version 4.0. Classic continues to provide a higher data rate for products requiring a constant connection, such as your headphones. The latest Bluetooth 5 revision continues down this path, splitting its improvements for Classic and Low Energy.
This update places a heavy emphasis on boosting the range and data rate of its low energy and long-range options. There is also an equally wide selection of radio power options that offer ranges varying from very short to over 100 meters, and these aren’t locked to any particular standard.
It caters to everything from file sharing and device pairing, to wireless music and industrial applications. Today, the standard is perhaps facing its biggest fork yet, with a dual focus on retaining backward compatibility while also powering increasingly low-energy IoT devices and broad communication mesh networks.
When Were Headphones Invented: The Complete History
In fact, the headphones industry earned around $34.8 billion in 2020 alone or sold as much as 514.5 million units in just one year! Let’s take a dive and see how headphone technology has evolved since the 1880s and what the future holds for this essential wearable tech. Back in the 1880s, switchboard operators used a type of “headphone” invented by Ezra Guilliland that could weigh over 10 pounds. Of course, back in the late 1800s, the use of earbuds or headphones for music listening was far off, and the technology’s application was limited to telephone use.
It looks similar to headphones we use today, except, instead of resting on the top of the head, they were handheld with a rod on the bottom connecting to the earpads. Not realizing the huge potential, Baldwin invented the first headphones in his kitchen in Utah as a device to help him hear the sermons at his local Mormon temple.
The Navy placed a large order of these headphones because of their design that didn’t need an external power source. A series of unwise investments and a stint in prison for mail fraud bankrupted his company.
These early headphones had plastic earcups, a 3-inch speaker, and foam earpads for comfortable wear.
For the first time, the market for headphones extended to include a teen audience and enter pop culture. In previous years, headphones remained as a listening equipment you use at home, mostly because they didn’t have a portable audio source. But while the technology changed the personal music scene, many users felt that the headphones that came with the Walkman (made from a single metal headband and 2 foam earphones) didn’t offer the best audio quality.
The history of noise-canceling headphones started years earlier, with various designs and patents dating back to the 1950s. This technology proved useful for pilots in the aviation industry, combat vehicle crewmen in the Army. With the rise of portable music devices like cassette tapes, CDs, and minidiscs, views on wearing headphones changed. By transmitting sound directly through the bones of the skull instead of the eardrum, these headphones allowed the user to remain connected to the outside environment.
In time, though, bone conduction headphones expanded to everyday consumers and athletes, with companies such as AfterShokz becoming well-known. There’s no doubt that by the turn of the century, Apple started pulling ahead of the pack in audio and technological advancements.
Just like what happened in the ‘80s with the emergence of the Walkman, the rise of the iPod and mp3 players led to a huge growth in the market for cheap, lightweight earbuds that has largely continued until today. While there had been extensive upgrades to headphones over the decades, one thing had pretty much always been consistent: wires connecting them to the audio source. Bluetooth technology had been under development since 1999, but while early versions could support voice calls, the bandwidth couldn’t handle streaming studio music. Over the past 20 years, various Bluetooth versions and upgrades have been released, allowing users to connect to their music wirelessly.
Beats by Dre became a powerful fashion statement and status symbol, especially after gaining popularity with top NBA players today. The link between headphones and fashion has continued, with hundreds of styles available today for different functions and preferences.
Now, with truly wireless headphones, everything was contained within the earbuds, including the on/off switch, mic, and volume control. While Onkyo may have released the first truly wireless headphones, it didn’t make a bigger impact than Apple’s AirPods. After their huge success among consumers, more manufacturers and brands have come up with their own versions of AirPods, with some even copying their style outright.
Some headphones can now even act as heart rate monitors, hearing protection devices, or even personal coaches for training or workouts.
The earbuds or headphones of the future could become an all-in-one device to both store, stream, and play music. It might seem crazy to think of today, but what if the headphones of the future looked more like hearing aids – more of a permanent device than one we carry around with us and have to put on and take off?
Over the years, we can expect greater things and additional functions for headphones in our day-to-day lives.
The History of the Headphone
He studied at Brigham Young Academy (BYA) and finished his electrical engineering degree at Stanford University. John Koss’ SP3 Stereophones started when patients from Milwaukee hospitals rented his portable phonograph. The revolutionary Koss SP3 Stereophones was proven to have good sound quality and were excellent for listening to music. Today, the established company of John Koss, located in Milwaukee, is still operating and producing headphones.
Sony, which is still a well-known company today, developed the ‘Walkman.’ The MDR-3L2 headphone was included with their cassette players. This helped block outside noises and assured the user a quality time listening to their favorite artists.
Dr. Amar went home disappointed and determined to develop a set of headphones with his own company – the Bose Corporation. Popular hip-hop artist and music producer – Dr. Dre – worked with Jimmy Lovine, who’s the Chairman of Interscope.
History of Truly Wireless Earphones
Gone are the days where we spent our precious time untangling the crumpled and twisting the irritating earphone wire that ended up spoiling our entire mood before we even began watching our flick or listening to our favourite artist! Once all the major brands like Apple, Samsung, Google, Oneplus, Oppo, Hammer, Boat, and many others stepped up and created this whole new category of earphones which were completely wireless and offered the best, hassle-free, and convenient audio experience.
The TWS earphones were finally affordable and offered a good price to quality ratio and that too through various forms of factors and feature sets.
When Were Headphones Invented: The Complete History
In fact, the headphones industry earned around $34.8 billion in 2020 alone or sold as much as 514.5 million units in just one year! Let’s take a dive and see how headphone technology has evolved since the 1880s and what the future holds for this essential wearable tech. Back in the 1880s, switchboard operators used a type of “headphone” invented by Ezra Guilliland that could weigh over 10 pounds. Of course, back in the late 1800s, the use of earbuds or headphones for music listening was far off, and the technology’s application was limited to telephone use. It looks similar to headphones we use today, except, instead of resting on the top of the head, they were handheld with a rod on the bottom connecting to the earpads. Not realizing the huge potential, Baldwin invented the first headphones in his kitchen in Utah as a device to help him hear the sermons at his local Mormon temple. The Navy placed a large order of these headphones because of their design that didn’t need an external power source. A series of unwise investments and a stint in prison for mail fraud bankrupted his company.
These early headphones had plastic earcups, a 3-inch speaker, and foam earpads for comfortable wear. For the first time, the market for headphones extended to include a teen audience and enter pop culture. In previous years, headphones remained as a listening equipment you use at home, mostly because they didn’t have a portable audio source. But while the technology changed the personal music scene, many users felt that the headphones that came with the Walkman (made from a single metal headband and 2 foam earphones) didn’t offer the best audio quality.
The history of noise-canceling headphones started years earlier, with various designs and patents dating back to the 1950s. This technology proved useful for pilots in the aviation industry, combat vehicle crewmen in the Army. With the rise of portable music devices like cassette tapes, CDs, and minidiscs, views on wearing headphones changed. By transmitting sound directly through the bones of the skull instead of the eardrum, these headphones allowed the user to remain connected to the outside environment.
In time, though, bone conduction headphones expanded to everyday consumers and athletes, with companies such as AfterShokz becoming well-known. There’s no doubt that by the turn of the century, Apple started pulling ahead of the pack in audio and technological advancements.
Just like what happened in the ‘80s with the emergence of the Walkman, the rise of the iPod and mp3 players led to a huge growth in the market for cheap, lightweight earbuds that has largely continued until today. While there had been extensive upgrades to headphones over the decades, one thing had pretty much always been consistent: wires connecting them to the audio source.
Bluetooth technology had been under development since 1999, but while early versions could support voice calls, the bandwidth couldn’t handle streaming studio music. Over the past 20 years, various Bluetooth versions and upgrades have been released, allowing users to connect to their music wirelessly. Beats by Dre became a powerful fashion statement and status symbol, especially after gaining popularity with top NBA players today. The link between headphones and fashion has continued, with hundreds of styles available today for different functions and preferences.
Now, with truly wireless headphones, everything was contained within the earbuds, including the on/off switch, mic, and volume control. While Onkyo may have released the first truly wireless headphones, it didn’t make a bigger impact than Apple’s AirPods.
After their huge success among consumers, more manufacturers and brands have come up with their own versions of AirPods, with some even copying their style outright.
Some headphones can now even act as heart rate monitors, hearing protection devices, or even personal coaches for training or workouts.
The earbuds or headphones of the future could become an all-in-one device to both store, stream, and play music. It might seem crazy to think of today, but what if the headphones of the future looked more like hearing aids – more of a permanent device than one we carry around with us and have to put on and take off?
Over the years, we can expect greater things and additional functions for headphones in our day-to-day lives.
All ears! A pictorial history of Bluetooth headsets. Part 1
It may be named after a 10th-century Danish king with a passion for tooth-staining blueberries, but Bluetooth is now very much a 21st century technology. Ten years ago they made you look like a Trekkie and gave you little more than fifteen minutes of talk time.
Nonetheless it served as a platform for the development of BT audio, use cases and user experience and is a crucial part of Nokia’s Bluetooth history. It hit the shelves in April and a year or so later it was replaced with the engine colored update, the HDW-3. It has BT HS, HFP, A2DP and AVRCP profiles, FM RDS radio, caller ID, track name, MP3 direct streaming, radio station names, indications from SMS, missed calls and a clock synchronized from the phone. So we took an earlier concept design and reduced it by innovating Printed Wireless Board technology.
If so, keep an eye out for Part 2 of Olli-Pekka’s history to see how the amazing evolution has continued until the present day.
Headphones: A History of the Original Wearable Tech
Early headphones may have been somewhat quaint by today’s standard, but the fundamental technology has been around for more than a century now and hasn’t actually changed all that much. 454,138 for, “improvements in telephone-receivers…which shall be light enough to be carried while in use on the head of the operator.” After some serious testing and refinement, Mercadier was finally able to produce miniature receivers that weighed less than 1 3/4 ounces (about 50 grams). Amazingly, Mercadier’s earphones even had a rubber cover, “to lessen the friction against the orifice of the ear… effectually close the ear to external sounds.” In 1906, according to a full-page advertisement in a London telephone directory, there were 14 theaters which subscribers could listen in on any given night, while on Sundays there were 15 different church services they could dial into. While the electrophone was gaining in popularity on the other side of the Atlantic, Nathaniel Baldwin was sitting at his kitchen table in Utah in 1910, tinkering with coiled copper wiring. Using more than a mile (1.6 km) of wire per earcup, Baldwin had been hoping to find a way to amplify the sound of sermons at his local Mormon temple.
“The military’s deployment of these headphones, which sailors used to isolate sounds broadcast from distant locations, lent them a more intense, solitary aesthetic than the hand-held Electrophone headset,” according to SSense. “An antennae-shaped brass spoke on each earphone, which allowed the headset to be adjusted to various sizes, completed the Jules Verne-esque steampunk look.” The book Gramophone, Film, Typewriter, written by Friedrich Kittler, describes the innovative radar system used by the German Airforce during World War II. This system allowed headphone-wearing pilots to reach their destinations, and bombers to accurately drop payloads without visually seeing their targets.
“Radio beams emitted from the coast facing Britain…formed the sides of an ethereal trailing the apex of which was located precisely above the targeted city. Built with design in mind, this model would prove to be incredibly popular and was enough to make the company shift focus from film equipment to audio gear.
Originally meant to demonstrate the quality of his company’s portable record player–which had a nifty private-listening switch–Koss’ headphones proved to be incredibly popular, just as rock and roll took over the music industry. Just prior to this, in the late-1950s, a company called Stax debuted the world’s first-ever pair of electrostatic headphones. Jettisoning the thick foam cup, the Sennheiser HD414 headphones using an open design, making them lighter and much less bulky.
As Sony was launching a new music revolution with the Walkman in 1979, Dr. Amar Bose was inspired by the awful quality of the headphones given to passengers during air travel.
Apple ended up shipping 600 million sets of first-gen earbuds, launching trillions of knock-offs in the process. Designed to bring back the bass-heavy sound of the older headsets for a new rap and hip-hop influenced music scene, the old over-the-ear earcups made a comeback after nearly a generation of confinement to the homes of dedicated audiophiles.
It wasn’t until 2016, when Bragi’s The Headphone, Jabra’s Elite Sport, and Apple’s AirPods came along, that the technology actually worked the way it was supposed to. Since then, many aftermarket manufactures have jumped on the bandwagon, and you can now pick up a fairly decent pair for a price that won’t break the bank.
These headphones claim to provide superior sound quality, capacitive touch controls, on-the-move communication, all-day connectivity, and much more.
“Our goal was to create all-in-one headphones that are compatible with every aspect of a user’s day, whether they’re at home, commuting, or in the office. “We’re excited to launch Human Headphones and bring customers a one-of-a-kind device equipped with the latest technology to deliver a seamless listening experience from morning to night,” he added. The integration of renewable charging, smart wearable solutions, and innovations in hearing protection is another potential future direction for technology.
It is also quite plausible that the future may well include a custom-fit headphone or earbud design tailored to the unique shape of each consumer’s ear, especially as 3D printing continues its penetration into society. Through their long history, headphones have always retained their essential function of helping to deliver the soundtrack to our lives.
The history of true wireless earbuds: Here’s what’s changed over the last six years
These days, the best wireless earbuds offer the same caliber of sound as their wired counterparts from five years ago while delivering rock-solid connectivity, useful extras like noise isolation, IP rating, digital assistant integration, and more. German startup Bragi started its crowdfunding initiatives on Kickstarter for the Dash back in February 2014, picking up over $3.3 million in just 45 days from nearly 16,000 backers. Earin started a Kickstarter campaign for its wireless earbuds back in June 2014, easily blowing past its funding goal of $300,000 just 10 days and eventually crossing $1 million.
As Bragi and Earin were duking it out to get the first true wireless earbuds to market, Japanese audio giant Onkyo showed off its first product in this category back at IFA 2015.
But by 2016, more brands started paying attention to the true wireless segment, with Samsung introducing its first offering in this category in the form of the $200 Gear IconX. These wireless earbuds were aimed at the fitness segment and had sensors to monitor heart rate, distance traveled, and calories burned, but the two-hour battery life made them a nonstarter.
While Samsung and Motorola’s fledgling attempts didn’t gain much momentum, Bragi launched a follow-up to the Dash called The Headphone, offering six-hour battery life and much more reliable connectivity. That wasn’t by coincidence; Apple intentionally ditched the jack to sell AirPods as a wireless alternative, and a big part of their success came down to this decision. Jitesh Ubrani, IDC’s Research Manager for Worldwide Mobile Device Trackers, says that the introduction of the AirPods acted as a “springboard” for customers and brands.
The $200 IconX (2018) didn’t have any connectivity issues either, and while it was still aimed at fitness enthusiasts, it doubled as a great option for normal use. However, the earbuds had fit issues, noticeable video latency, sub-par noise isolation, and average battery life. The true wireless segment went into high gear in 2018, with audio brands delivering refined products with no glaring shortcomings.
Jabra’s Elite 65t set the standard early on, with the $170 wireless earbuds offering superb sound quality backed by an easily customizable fit, Bluetooth 5.0 connectivity, five-hour battery life, and a pocketable case. Then Sennheiser made its foray with the $300 Momentum True Wireless Earbuds, setting a new standard for sound quality in this segment.
As Bluetooth 5.0 proliferated on budget Android phones and earbuds alike, wireless connectivity issues would soon be a thing of the past. With sound quality still being the biggest consideration in this segment, brands started turning to high-fidelity Bluetooth audio codecs like AptX HD and LDAC to give their offerings an edge. Samsung redoubled its efforts in this category with the launch of the $130 Galaxy Buds, rolling out much-needed upgrades: six-hour battery life, wireless charging, and an easily pocketable case. 2019 was a particularly great year for wireless earbuds, with the high-end segment fielding excellent options like the Sony WF-1000XM3, Jabra Elite 75t, and the Beats Powerbeats Pro. The WF-1000XM3 stood out for the exceptional noise cancellation combined with the sound quality, the Elite 75t were a great all-around choice, and the Powerbeats Pro somehow managed to last nine hours from a full charge. In fact, 2019 is when most Chinese phone manufacturers started getting into true wireless earbuds, leading to a wave of budget-focused models that lowered the barrier to entry for this category.
Xiaomi led the way with a slate of budget wireless earbuds that debuted for under $50, and OPPO soon followed with its Enco series, undercutting the likes of Samsung and Sony.
The U.S.-based brand leveraged its Soundcore label to roll out affordable wireless earbuds with great sound quality and exciting features. Wireless earbuds have matured in a relatively short amount of time, and in 2021, this increasingly crowded category includes hundreds of great options that start as low as $15 and go all the way to $900. As a result, the wireless audio segment racked up over 300 million sales in 2020, and that number is set to increase significantly in the next two years.
Headphones
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. Another type, known as earbuds or earpieces[1] consist of individual units that plug into the user’s ear canal. 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. Initially the audio quality was mediocre and a step forward was the invention of high fidelity headphones.
Some stereo earbuds are wireless, using Bluetooth connectivity to transmit the audio signal by radio waves from source devices like cellphones and digital players. 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. Nathaniel Baldwin of Utah in 1910 invented a prototype telephone headset due to his inability to hear sermons during Sunday service. 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. 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 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. In early powered radios, the headphone was part of the vacuum tube’s plate circuit and carried dangerous voltages.
Smaller earbud type earpieces, which plugged into the user’s ear canal, were first developed for hearing aids. 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. 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. 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, which splits the audio signal to share with another participant, but can also be used to hear audio from two inputs simultaneously. [13] 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. Circum-aural earphones are also used to establish hearing thresholds in the extended high frequency range (8,000 Hz to 20,000 kHz). Calibration is done with the earphones in an acoustic coupler that is intended to mimic the transfer function of the outer ear. In recent years, impedance of newer headphones has generally decreased to accommodate lower voltages available on battery powered CMOS-based portable electronics.
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). Higher impedance headphones are more tolerant of amplifier limitations, but produce less volume for a given output level.
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. The maximum sound pressure level is a matter of preference, with some sources recommending no higher than 110 to 120 dB. [20] 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. Generally, headphone form factors can be divided into four separate categories: circumaural (over-ear), supra-aural (on-ear), earbud and in-ear. [22] 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.
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.
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.
Among applications for headsets, besides telephone use, are aviation, theatre or television studio intercom systems, and console or PC gaming. Most models of telephone amplifiers offer volume control for loudspeaker as well as microphone, mute function and switching between headset and handset. 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. Electrostatic drivers consist of a thin, electrically charged diaphragm, typically a coated PET film membrane, suspended between two perforated metal plates (electrodes). Air is forced through the perforations; combined with a continuously changing electrical signal driving the membrane, a sound wave is generated. 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.
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. A planar magnetic driver consists of a relatively large membrane that contains an embedded wire pattern.
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. The design is not mechanically stable; a slight imbalance makes the armature stick to one pole of the magnet.
[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. [29] 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. In 2013 a carbon nanotube thin-yarn earphone based on the thermoacoustic mechanism was demonstrated by a research group in Tsinghua University. 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 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. 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. 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.
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. They allow call center agents to maintain better posture without needing to hand-hold a handset or tilt their head sideways to cradle it. 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.
“[37] 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. Most major manufactures of smartphones now include some safety or volume limiting features and warning messaging in their devices. [39][40] though such practices have received mixed response from some segments of the buying who favor the personal choice of setting their own volume levels. 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. 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.) 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 published several documents targeted at protecting the hearing of workers who must wear communication headsets such as call center operators,[46] firefighters,[47] and musicians and sound engineers.
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