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How do headphones work? What's inside them? - Explain that Stuff
`
`5/15/21, 9:44 AM
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`Headphones
`
`I C
`
`by Chris Woodford. Last updated: April 14, 2021.
`
`f you've ever been to a rock concert and heard music thumping out of giant loudspeakers,
`you'll know sound can pack a powerful punch. Sometimes, however, we want to enjoy
`music more quietly and intimately or in places where others don't want to hear what we're
`listening to. Trains and planes are noisy enough—just imagine the cacophony there would be if
`everyone sat with massive stereo systems in front of them! For times like this, headphones let
`us retreat quietly into our own imaginary worlds. Let's take a closer look at what's inside them
`and how they work!
`
`Photo: My open-backed Sennheiser HD-485 headphones. Most of what you see in this photo is cosmetic: it adds little
`or nothing to the quality of the sound you hear. But it's important to remember that headphones have to be
`comfortable to wear for a reasonable amount of time or they'll be a waste of your money. The softly padded earpieces
`and foam padding across the top of the headband make these very comfortable. The plastic they're made from is light
`enough not to press on your head, but strong and durable enough to withstand wear and tear. Another cool feature is
`the removable lead: there's a jack plug where the wire joins onto the body of the headphones, which you can easily
`remove and replace.
`
`ontents
`
`1. Headphones: miniature
`
`Headphones: miniature
`loudspeakers fixed to your ears
`
`https://www.explainthatstuff.com/headphones.html
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`How do headphones work? What's inside them? - Explain that Stuff
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`5/15/21, 9:44 AM
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`loudspeakers fixed to your
`ears
`2. How earbuds work
`3. How bigger headphones
`work
`4. Who invented
`headphones?
`5. Buying headphones
`6. Find out more
`
`Headphones (which are often called "cans" by DJs and
`people who work in radio broadcasting) work in exactly the
`same way as speakers, so you might want to consult our
`article on loudspeakers if you're not sure how they use
`magnetism to turn electrical energy into sound.
`
`The biggest difference between loudspeakers and
`headphones is, of course, size. A loudspeaker needs to
`set all the air moving in a room so you can hear the sound
`it's making, but the speaker in a headphone only has to
`move the volume of air inside your ear canal. That's why it
`can be so much smaller and more discreet.
`
`Large headphones are essentially just two loudspeakers mounted on a strap that clamps firmly
`over your head. Earbuds work the same way but, as you would expect, everything inside them
`(the magnet, the coil of wire, and the diaphragm cone that makes sound) is shrunk down to a
`much smaller size.
`
`Speakers tend to be built into "enclosures" (as engineers call them—the rest of us call them
`"boxes") to amplify their sounds and keep them safe from damage. If you look closely, you'll see
`speaker enclosures usually have openings at the front or the back so air can move more freely
`in and out of them to generate decent sound. The same is true of headphones and earbuds,
`which come in two main types. As their name suggests, closed-back headphones are sealed
`at the back so (theoretically) no sound escapes (or leaks in from outside) while open-back
`headphones are open to the air at the back as well as the front. Many people find that open-
`back headphones sound better but much of the noise will leak into the room around you and
`annoy other people, while "ambient" noise from the room can easily penetrate open-back
`headphones and annoy you too. If that's a problem, you need closed-back headphones or
`noise-cancelling headphones, which make it easy to cut yourself off completely.
`
`How earbuds work
`Taking broken things apart is a great way to find out how they work. If you're a young person,
`ask an adult first to make sure what you want to dismantle is really safe.
`
`1. Here's my broken earbud and I've popped the back off it. You can see how the wires run
`up through the main case to the coil inside. We need two wires to make a circuit: one
`carries the current into the coil from the stereo; the other carries it back again.
`
`https://www.explainthatstuff.com/headphones.html
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`How do headphones work? What's inside them? - Explain that Stuff
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`5/15/21, 9:44 AM
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`2. Next, I've tipped the earbud over and popped the front cover off. The front cover is a
`plastic disc with holes in it to let the sound enter your ear. Just behind it there's a very
`small cone. It's hardly cone-shaped, though: it's a flattish, transparent disc made of very
`thin and flexible plastic, and it's quite crinkly and crackly when you move it. You can just
`see the tiny metal coil (colored red) attached to it.
`
`3.
`
`In summary, then, these are all the bits that make up your earbuds:
`Back case: holds everything together. The wires run up through a hole at the
`bottom.
`Front case: This is the part that faces into your ear. Sometimes it's covered with a
`little fabric pouch to keep it clean.
`Seal: This rubbery circle clips the front case to the back case, holding the two
`together.
`Wires: Carry signals from the stereo to the speaker.
`
`https://www.explainthatstuff.com/headphones.html
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`How do headphones work? What's inside them? - Explain that Stuff
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`5/15/21, 9:44 AM
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`Magnet: The permanent
`magnet at the back of the
`speaker. This is the heaviest
`part of an earbud and makes
`up the vast majority of its
`weight.
`Coil: This becomes an
`electromagnet when
`electricity flows through it.
`Transparent plastic cone:
`This makes the sound when
`it moves.
`
`How bigger headphones
`work
`As you might expect there's nothing radically
`different inside bigger headphones: they're
`just a scaled-up version of what you find
`inside earbuds.
`
`As luck would have it, the arrival of my new
`Sennheiser headphones was followed quite
`quickly by the final collapse of my old pair. I
`could have repaired them, my friends, but in
`the interests of your curiosity, they've agreed
`to leave their insides to medical science!
`
`Let's see what we find when we open them up:
`
`Sponsored links
`
`1. This is one of the two earpieces from my old pair of open-backed headphones with the
`light foam cover and the cable removed. Note that "open-backed" is a bit of an
`understatement for what you see here: the headphones are almost completely open to
`the air and built around a kind of plastic spoke design. The diaphragm that makes the
`sound is in the center. The open spokes radiating outwards are there to make the
`headphone the right size to cover your ear, without making it too heavy or
`uncomfortable.
`
`https://www.explainthatstuff.com/headphones.html
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`2. Now I've popped out the central part that contains the loudspeaker:
`
`3. Break off the protective plastic "spokes" and you can see the transparent plastic
`cone/diaphragm behind. You can also just see some small holes (beige dots) behind it
`that let sound out of the back and allow the diaphragm to move back and forth more
`freely.
`
`4. Now the painful part. Break open the diaphragm cone (it's much thicker plastic than the
`ones in earbuds) and you can see the coil (red band) fastened on to it and the
`permanent magnet (silver and gold) behind. The coil sits in the slot like a band running
`loosely around the outside of the magnet:
`
`https://www.explainthatstuff.com/headphones.html
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`5. Here's another shot of the diaphragm cone and the coil:
`
`You can find bigger and clearer versions of these photos on our Flickr.
`
`Who invented headphones?
`And why? Early loudspeakers were pretty cumbersome things, and in the late 19th and early
`20th century, when audio equipment was equally cumbersome, there was no obvious,
`immediate reason to shrink "sound reproducing machines" down to the size of your ear. So how
`and why did headphones and earbuds come about? There were three reasons, essentially.
`
`First, headphones and earbuds can reproduce sound with much less input power than big
`loudspeakers, so they work very well with unsophisticated, low-powered, audio equipment. If
`you've ever built a crystal radio, you'll know you can do it without a battery or power source of
`any kind providing you use what's called a crystal earpiece, which generates sound through
`piezoelectricity using very little input energy (from the incoming radio waves). Some early
`earpieces were even less sophisticated. You could listen to Thomas Edison's sound-recording
`phonograph (the forerunner of modern record players) using either an amplifying "horn"
`(ancestor of the loudspeaker) or stethoscope-like tubes stuffed in your ears (ancestors of the
`earbud).
`
`Second, despite the cumbersome nature of audio equipment, there was still a pressing need for
`
`https://www.explainthatstuff.com/headphones.html
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`portability. Back in 1891, a Frenchman named Ernest Mercadier patented a "bi telephone" (a
`pair of in-ear telephone receivers) that look strikingly like modern headphones, "which shall be
`light enough to be carried while in use on the head of the operator, and, second, an improved
`means for securing the same in place." Portability was clearly a must for the military; one of the
`key reasons for developing headphones was that pilots and battlefield soldiers had to hear
`sound clearly and discreetly. You couldn't put giant loudspeakers in the cockpit of a noisy, World
`War II fighter plane!
`
`Photo: The military need for clear, effective, discreet comunication was a major driver of headphone development.
`Photo by Joshua J. Seybert courtesy of US Air Force.
`
`Finally, not everyone can hear sound from loudspeakers as clearly as you might be able to.
`Leafing through the patents in the US Patent and Trademark Office database, it's clear that
`some of the earliest earbuds were actually earpieces attached to hearing aids. If you want to
`amplify sound, and do it portably and discreetly, using an earpiece makes a lot more sense than
`using a loudspeaker. Apart from putting the sound directly in someone's ear, you also separate
`the microphone from the speaker and so help to reduce "buzzing" and "whistling" (where the
`speaker effectively feeds back into the microphone). In 1943, for example, several years before
`transistors completely revolutionized the power of hearing aids, we have Zenith Electronics
`offering a hearing aid earpiece with just these aims in mind.
`
`Buying headphones
`
`You can tell what a new pair of jeans will look like without even pulling them on. But
`how on Earth can you tell what a pair of headphones is going to sound like without
`
`https://www.explainthatstuff.com/headphones.html
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`How do headphones work? What's inside them? - Explain that Stuff
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`5/15/21, 9:44 AM
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`listening first? Buying headphones involves guesswork and good luck, but follow
`these simple tips and you won't go far wrong.
`
`Photo: Noise-isolating Etymotic earbud
`headphones. The rubbery gray flanges make
`a tight seal inside your ears and stop sounds
`getting in or out. The sound quality is far
`superior to that from normal earbuds. These
`earbuds come with different kinds of
`earplugs: the washable flanges you see here
`and disposable foam ends that are more
`comfortable but need replacing periodically.
`Both kinds have to be pushed into your ear
`canals to cancel background noise
`effectively—and they can get uncomfortable
`after a while.
`
`Try before you buy
`Inexpensive earbuds usually come heat-sealed in tough plastic, so even if you can
`try your new phones, there's no way you can return them if you don't like them.
`That's why it's best to buy headphones from a hi-fi shop if you possibly can. Quite
`often they have a few different demonstration pairs you can test out. There's nothing
`to stop you testing headphones in a shop and buying online later if you can get a
`better deal—though ask the store first if they'll match the price. Alternatively, ask a
`few of your friends what they use and listen to their headphones. Aim to try at least
`three or four different pairs.
`
`If you're determined to buy online, remember that reviews can be misleading and
`unhelpful; they might even be planted by retailers or manufacturers. Sound is very
`personal and one person's idea of acoustic heaven might be another's idea of noisy
`hell. Different types of music exploit different parts of the sound spectrum (drum and
`bass will necessarily make heavier use of lower frequencies than classical music),
`so one pair of headphones might not sound equally good for everything you listen
`to. If you're going to go by online reviews, read widely and critically, and check well-
`informed professional reviews on audio sites as well as off-the-cuff amateur
`opinions.
`
`Beware the bass
`
`Photo: A pair of earbud phones from an MP3 player. The metal gauze on the front is "acoustically
`transparent": it lets sound out without letting (too much) dirt and dust in. The backs of some earbuds
`are completely sealed to stop sound from escaping (so they're similar to closed-back headphones),
`though other earbuds do have small vent holes in them (making them equivalent to larger, open-backed
`headphones).
`
`https://www.explainthatstuff.com/headphones.html
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`How do headphones work? What's inside them? - Explain that Stuff
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`5/15/21, 9:44 AM
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`Since Walkmans took off in the
`1980s, there's been a trend for
`making headphones (and earbuds)
`sound very bassy at the expense of
`decent fidelity aross the entire range
`of frequencies; that biases people's
`expectations of how headphones
`should sound, which, in turn,
`prompts manufacturers to produce
`bass-heavy models that satisfy the
`demand (see, for example, Steve
`Guttenberg's article How do you like your headphone sound: Accurate or bassy?).
`Mass-market phones and earbuds may well be designed to emphasize bass
`frequencies—which is great if that's what you like and horrible if not. Beware of
`products that draw too much attention to their "bass response."
`
`Listen to your own music on your own equipment
`
`Both your hi-fi (or music player) and the headphones will affect the quality of the
`sound you hear, so if you're trying to compare headphones make sure you use the
`same stereo equipment in each case—and listen to familiar music. If you're trying
`expensive headphones in a hi-fi shop, take in your own equipment—even a portable
`CD player or MP3 player is better than nothing. The quality of MP3 tracks is always
`poorer than that of the same tracks played from a CD (because MP3 is a
`compressed digital format). In other words, a pair of headphones will sound worse
`with an iPod or MP3 player than with a CD player, even when they're playing the
`same track. So test headphones with a CD player if you possibly can.
`
`Big headphones or small earbuds?
`
`Think about where you're likely to use headphones—and how. Is the portable
`convenience of earbuds more important than the (likely) higher fidelity of
`headphones? Big headphones that sit over your ears generally sound better than
`small earbuds—that's why DJs wear "cans" (big phones). Having said that, there
`are high-quality, very expensive earbuds just as there are high-quality headphones.
`If you want some phones for listening mainly on the move (or for listening to a
`portable stereo or MP3 player at home), earbuds are generally the best bet; bigger
`headphones are usually better for "audiophiles" who want to listen to music or TV
`without disturbing (or being disturbed by) other people.
`
`https://www.explainthatstuff.com/headphones.html
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`How do headphones work? What's inside them? - Explain that Stuff
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`5/15/21, 9:44 AM
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`Open or closed headphones?
`
`Open-backed phones usually sound better to me than closed-back ones, because
`they let sound move more freely with less distortion inside. If you're buying phones
`for private home listening in a room where other people will be chattering away or
`listening to the TV, you may prefer a closed-backed pair. Similarly, if you intend to
`use your phones on a train, bus, or plane, closed-backed headphones will reduce
`the background noise you hear and the disturbance you cause to other people—
`although noise-canceling headphones are generally better for travel use.
`
`Normal or noise-canceling headphones?
`
`If you're listening to headphones in a noisy place (on a plane or in a noisy home),
`background sounds can seriously reduce the quality of the experience. Noise-
`canceling phones can be a big help and they come in two main kinds. Passive
`noise-isolating earbuds (like Etymotics) have earpieces that make a seal with your
`ear canal, preventing unwanted sound from getting in. Active noise-reduction
`headphones and earbuds (such as Bose QuietComfort) have a little microphone on
`the outer case. The microphone samples the background noise and an electronic
`circuit inside the phones automatically compensates for it (read more in our article
`on how noise-canceling headphones work). Passive noise-isolating earbuds are
`very low-tech and very effective; active noise-canceling phones can be more
`comfortable to wear, but generally need their own battery power (so you have an
`added, ongoing cost if you're going to use them regularly). If you're listening in a
`quiet place at home, there's no real reason to buy noise-canceling headphones:
`they tend to be much more expensive and, for the same price as a pair of noise-
`canceling phones, you could probably get a much higher quality pair of normal
`phones.
`
`For safety reasons, don't under any circumstances use them on a bicycle,
`skateboard, or while driving a car—you won't hear things around you. You can buy
`bone-conduction headphones for use on bicycles and boards, which work by
`transmitting sound through the bones in your skull, but I'm not sure I would risk it.
`
`What sized jack plugs do headphones have?
`
`Earbuds have small jack plugs (usually 3.5 mm or 1/8"), while bigger headphones
`typically have plugs about twice the size (typically 6.3mm or 1/4"). If you buy cheap
`earbuds, you won't be able to use them on a big stereo or TV unless you buy an
`adapter to go with them (those are relatively easy to find online or in hi-fi stores—
`
`https://www.explainthatstuff.com/headphones.html
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`5/15/21, 9:44 AM
`
`just type "3.5 mm to 6.3mm headphone adapter" into Google). Conversely, however,
`most decent audio headphones with 6.3mm plugs come ready-supplied with 3.5mm
`adapters so you can use them on smaller equipment too.
`
`Build quality matters
`
`Earbuds and headphones almost invariably fail where the main cable meets the jack
`plug (and, occasionally, where the cable meets one headphone/earbud or the
`other). If I were cynical, I might suggest headphone makers deliberately engineer
`their products to fail by using poor-quality cables and connections. You can always
`tell a good pair of headphones: the makers will have devoted some time to making
`sure the connections are robust enough to cope with constant flexing of the cable.
`Though you can't easily detect headphones and earbuds with poor connectors, you
`can spot well-engineered connections. Look out for makers who draw attention to
`any efforts they've made to make their cables more durable. If your headphone
`cable does fail, and you know how to use a soldering iron, it's relatively easy to fit a
`new jack plug—you can double the life of your phones with about 10 minutes' work;
`repairing headphone cables at the other (earphone) end is much more tricky and
`often not worth the effort. Hi-fi shops can sometimes also do repairs for you. (See
`our article on how to repair headphones for more details.)
`
`In my view, coiled cables are a mixed bag. On the positive side, they save you
`having to keep wrapping up your headphone cable. On the negative side, coiled
`cables are virtually always stretched open and that constant tension puts added
`strain on the weakest points of the cable, where they meet the jack plug and the two
`headphones. Generally, I prefer to use an uncoiled cable and an extension lead.
`
`Photo: Sick of broken headphone cables?
`Here's the ultimate solution: buy headphones
`with a detachable cable. You can unplug the
`cable from the headphone end as well as
`from the other end. If your cable fails, you
`simply unplug it and buy a replacement!
`These are Sennheiser HD-485s.
`
`You get what you pay for
`
`The basic rule of buying things
`generally holds true of
`loudspeakers, headphones, and earbuds. If you study the wide range of phones
`offered by a decent manufacturer like Sennheiser, you'll notice a distinct correlation
`between quality and price: the low-end phones are good, basic, and relatively
`inexpensive; the high-end phones are recording-studio quality and cost many times
`
`https://www.explainthatstuff.com/headphones.html
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`more.
`
`Portable music players come with their own "default" headphones, but there's no
`reason why you have to stick with them. Try some others and you might be
`surprised how much better—or different—your music sounds: you might hear
`instruments or effects you didn't notice before. Shortly after buying an iPod, I
`switched to using some expensive Etymotic earbuds (which cost almost as much as
`the iPod)—and they made a huge difference to the sound quality. But remember
`that MP3 players are inherently limited in audio quality by the compressed files
`they're playing. If you want to hear better quality sounds, go back to your CD
`player... or even vinyl LP records!
`
`Sponsored links
`
`Find out more
`
`On this website
`
`https://www.explainthatstuff.com/headphones.html
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`How to repair earbud headphones
`Loudspeakers
`Noise-cancelling headphones
`Sound
`
`On other websites
`
`Headphone safety: Acoustic engineer Tony Woolf explains how to use headphones and
`earbuds sensibly so you don't damage your hearing.
`
`Books
`
`Loudspeaker and Headphone Handbook by John Borwick. CRC Press, 2012. A detailed
`technical referenced aimed at sound-industry professionals.
`
`Articles
`
`Your Earbuds Will Become Your Most Powerful Health Monitor by Stacey Higginbotham.
`IEEE Spectrum, 21 March 2019. Sensors fitted to headphones could soon be monitoring
`your vital signs!
`How to choose the best wireless headphones by Alan Henry. The New York Times, 3
`October 2017. Bluetooth wireless headphones are now seriously worth considering.
`AI in your earphones? The brave new world of hearables by Sean Hargreaves. The
`Guardian, 29 June 2017. Future earbuds will block noise, improve your hearing, and
`maybe even translate foreign languages.
`Wireless Earbuds Will Record Your EEG, Send Brainwave Data to Your Phone by Eliza
`Strickland. IEEE Spectrum, 17 May 2016. Will your earbuds soon be tracking your brain
`activity?
`Who made that earbud? by Daniel Engber. The New York Times, 16 May 2014. More
`than half of all earbuds sold (by revenue) are earbuds. Surprisingly, the idea dates not
`from the 1990s but the 1890s!
`What makes a pair of headphones good? by Spencer Kelly and Richard Taylor. BBC
`News, 15 March 2012. A video guide to choosing headphones that make your audio
`equipment sound better.
`Bike headphones that don't distract from cycling safely by Laura Laker. The Guardian,
`
`https://www.explainthatstuff.com/headphones.html
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`26 March 2012. Is it possible to cycle safely and listen to music at the same time? A
`quick look at bone-conduction headphones.
`Why spend £1,000 on headphones? by Alex Hudson. BBC News, 16 August 2011. Are
`expensive headphones really worth the investment?
`Will sport headphones pass Simon's test? by Simon Gompertz. BBC News, 22
`September 2009. A jogger compares different brands of sports headphones.
`White noise by Jonathan Duffy. BBC News, 5 January 2006. Explains how lengthy use of
`earbud headphones may be damaging your hearing and the sensible precautions you
`can take to reduce the risk.
`
`Patents
`
`There are hundreds of patents covering all kinds of headphone and earbud designs—and
`they're well worth looking at for deeper technical insights. Here's a representative selection to
`give you a taste:
`
`US Patent 1,601,063: Acoustic Device by Halsey A. Frederick. Western Electric, 28
`September 1926. One of the earliest patents I've found for "earbud" headphones,
`designed either for hearing aids or telephone receivers. Despite the age of the invention,
`you can see that this earphone is built in essentially the same way as a modern one.
`US Patent 2,353,070: Headphone by Roy Pitkin, 4 July 1944. A typical pair of sound-
`isolating, military headphones designed for aviators during World War II. They have
`large padded cushions to prevent outside noise from interfering with the noise generated
`by the loudspeakers.
`US Patent 5,095,382: Wireless Headphone by Kensasku Abe, Sony Corporation, 10
`March 1992. An early wireless headphone using infrared to beam sounds from a
`transmitter to a wireless headset.
`US Patent 8,265,328: Earphone by Lars Milde and Markus Kuhr, Sennheiser Electronic,
`11 September 2012. A modern earhook earbud.
`
`Please do NOT copy our articles onto blogs and other websites
`
`Articles from this website are registered at the US Copyright Office. Copying or otherwise using registered works
`without permission, removing this or other copyright notices, and/or infringing related rights could make you liable to
`severe civil or criminal penalties.
`
`Text copyright © Chris Woodford 2006, 2021. All rights reserved. Full copyright notice and terms of use.
`
`https://www.explainthatstuff.com/headphones.html
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`Page 15 of 15
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`Apple v. GUI Global Products
`IPR2021-00472 GUI Ex. 2014
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