Learn About Headphones

Background

Many people today use headphones and earbuds. These are accessories connected to different devices like mobile phones and computers to hear sounds. Most of the time, they are used for listening to music or watching movies, but they can also be used for other purposes, such as when calling or answering calls on a smartphone, when recording music, and more.

Headphones and earbuds today are mostly used to avoid distracting other people when you want to listen to certain songs or watch movies in a certain place. This made headphones an absolute necessity in the daily lives of many people today. Also, at the present time, there are many different types of headphones and earbuds you can find in the market. Most of them are high-tech and can be connected to different devices wirelessly.

With this, have you ever thought about how these accessories began? How many people in the world do you think uses headphones and earbuds? If you have the same questions in mind, you’re in the right place. In this post, we are giving you more information about headphones and earbuds, including their histories, different types, numerical data and statistics about them, and some mind-blowing facts that you need to learn about. Let us start with their history.

The History and Evolution of Headphones

Like any other technology out there, headphones did not become a huge and successful industry overnight. In fact, it took decades of innovation for it to turn into the headphones that we know and use today. If you are curious, let’s take a look at how headphone technology started and how it evolved.

Headphones in the 1880s

Today, a lot of people find big and bulky headphones quite bothersome to use. That’s why most of them look for smaller and lighter options. However, when you were around when the first headphones were made, there wasn’t any smaller option available for you.[1] Way before MP3s and online music streaming platforms were invented, headphones had little to do with music at all.

Back in the 1880s, the very first headphones, or at least their descendants, were utilized by telephone operators. It was a single earpiece that rested on the shoulder of the user, and it surprisingly weighed more than 10 pounds. That probably felt like placing a boombox on the shoulders.[2] That type of headphone was made by Ezra Gilliland.[1]

The First “Earbuds” in 1891

A French engineer named Ernest Mercadier patented the “bi-telephone” in 1891. It proves to be the first recorded version of in-ear headphones. It is a lightweight and portable device that closely resembles IEMs that people use today. This is quite interesting, considering it was invented hundreds of years ago. In fact, Mercadier even suggested using a rubber cover to protect the ear from friction while using them. Today, earphones are used mostly for music listening. However, back then, the technology’s application was limited to telephone use.[1]

The Electrophone in 1895

It is quite popular for us today to listen to music with friends online as there are many ways to do this. However, that was not the case a hundred plus years ago, before the radio was even invented. But still, people back then could do it. How? Through the electrophone. It was a subscription service in London that allowed users to listen to live theater performances via their telephone line.

Users of electrophones have specialized headphones connected to their telephone lines so that they can listen to the programs. It was like Spotify but for opera. The headphones they used back then looked similar to what we use today. However, instead of being worn on top of the head, they were handheld with a rod on the bottom connecting to the earpads, which look more like a stethoscope.[1] Due to this, people back in 1895 were able to enjoy the sounds from the opera house from the comfort of their own homes.[2]

The First Modern Headphones

a vintage headphone

In 1910, the first modern headphones were manufactured by Nathaniel Baldwin. They were crafted in his kitchen.[2] His invention included two padded ear cups and two bands across the head for it to comfortably sit on the head without using the user’s hands. The first headphones were made as a device to help him hear the sermons at his local Mormon temple.

The idea was ridiculed by initial investors without knowing its value until it was bought by the U.S. Navy. A large order of these headphones was placed by the Navy due to their design and that they did not require an external power source. It opened up a huge business opportunity for him. However, he did not patent it, and a series of unwise investments and a stint in prison for mail fraud caused bankruptcy in his company.[2]

The Start of Headphone Brands

Today, many audio brands are available in the market, such as Sennheiser and Philips. However, these brands all owe their start to John Koss. Back in the 1950s, headphones were not really available commercially. Their use was limited mostly to communication and the military. But that changed when 1958 came, and John Koss made a “private listening system,” which was the Koss Model 390 phonograph.

The system included a speaker, record player, and headphone jack. In addition to that, he also made headphones that would go with it, which were the Koss SP-3 headphones. It featured plastic earcups, foam earpads for comfort, and a 3-inch speaker. These were the first headphones that were made specifically for music listening. His innovation paved the way for more advancements in headphone technology.[1]

The First Wireless Headphones

vintage radio headphones

Wireless headphones and earphones are prevalent today via Bluetooth technology. But decades before they existed, wireless headphones had already invaded the market. These were available and widely used in the 1960s and 1970s. The very first wireless headphones were known as “radio headphones.” They use built-in AM and FM radio antennas and as well as 2 inches speakers in each padded earcup. They enabled users to bring their radio and listen wherever they wished. Back in those years, radios were a big deal. That’s why this model helped hearing-impaired individuals to hear their radios better, too.[1]

In 1966, John Koss made another innovation which was the Beatlephones. These were branded headphones with a partnership between Koss and The Beatles. Their collaboration was a marketing success. The market for headphones, for the first time, extended to include a teen audience, and it entered pop culture.

The First Open-Back Headphones

More changes came to the headphone scene in 1969, especially with the appearance of Sennheiser’s HD 414, which was the first open-back headphones. These feature open-back ear cups for the user to enjoy a wider sound. In addition to that, it also made the headphones lighter and more breathable. During this time, the audio quality of headphones improved, and people were able to use them more comfortably for longer periods.[1]

The Creation of the Walkman

a portable cassette player with headphones and cassette tapes

Headphones stayed as a piece of listening equipment used at home in the previous years because they did not have a portable audio source. But when the Walkman was introduced, listening to music became more personal and private. This gave people the ability to listen to their own music library instead of the radio. When the Walkman was released, cassette tapes outsold vinyl.

Sony introduced the Walkman in 1979, and it helped headphones get out of the house for the first time. It was small enough to carry around, and it was also very lightweight. This invention filled the need for portability in headphones. However, while technology changed the personal music scene, a lot of people felt that the headphones that came with the Walkman did not offer the best audio quality. With this, the demand for third-party headphones boomed. Sony’s invention paved the way for more headphone brands and competitors to enter the market.[1]

The Invention of Noise Canceling Headphones

man using noise-canceling headphones

In 1989, the use of headphones for private listening evolved more when noise-canceling headphones were invented. In fact, its history began earlier with different designs and patents that date back to the 1950s. However, these designs were not developed into what we know today until it was invented by Dr. Amar Bose, the founder of the popular audio company Bose.

These headphones work with a small microphone that captures all the outside noise and creates an equal, opposite sound wave to remove the noise. It was a technology that became very useful for pilots in the aviation industry and as well as for the combat vehicle crewman in the army. Eventually, noise-canceling headphones increased in popularity for personal use.[1]

The Creation of Smaller Technologies

Portable music devices continued to be released in the following years. These include cassette tapes, CDs, and as well as minidiscs. With this, the view on wearing headphones also changed. Instead of being used at home, people began to bring them on the go. With this, the people’s desire for a smaller and more portable headphone technology grew. When the 1990s came, this need was met when smaller and more portable types of headphones were released, including in-ear headphones, earbuds, neckband headphones, and more.

woman wearing bone conduction headphones

In 1994, Werner Bottesch patented the first bone conduction headphones. It was initially used for the military. It transmits sound directly through the bones of the skull instead of the eardrum. This way, the user will remain connected to the outside environment. Later on, its use expanded to everyday consumers and athletes.

In 2001, Apple began pulling ahead of the pack when it came to audio and technological advancements. One example of this is the iPod. Its release made way for portable digital music streaming, which made people move away from cassette tapes and CDs. The iPod was accompanied by the EarPods, which also innovated the industry with their sleek and modern aesthetic. The popularity of the iPod and mp3 players led to a huge growth in the market for affordable, lightweight earbuds that are still being used today.[1]

The Bluetooth Revolution

Over the decades, there have been extensive upgrades to headphones. However, one thing has pretty much always been consistent, and that is wires connecting them to the audio source. But in 2004, this changed when Bluetooth technology was invented. In fact, it has been under development since 1999. However, its earlier versions only supported voice calls as the bandwidth could not handle streaming studio music. Over the past 20 years, different Bluetooth versions and upgrades have been released, which allowed people to listen to music wirelessly.

woman wearing wireless in-ear headphones

Before 2015, wireless headphones and earbuds were used by many people. However, they weren’t entirely wireless. They did not have a wire to the audio source, but each earpiece is still connected with a wire. In 2015, Onkyo released the first truly wireless headphones, which was the Onkyo W800BT. Everything was found within the earbuds, including the on and off switch, volume control, and microphone.

person wearing AirPods

But what made a bigger impact was Apple’s AirPods, which was introduced in 2017. Apple also moved away from their wired earpods. The AirPods were very lightweight, and they introduced lots of new features, such as double-tapping to pause the audio and automatic pausing when they are removed from the ear. Since its release, it quickly became Apple’s most popular accessory. After its success, many other manufacturers and brands came up with their own versions of the AirPods.[1]

Headphones in the Future

In the last few decades, headphone technology has come a long way. Many smartphones today no longer have 3.5mm ports for headphones due to wireless technology. There are also some headphones today that can act as heart rate monitors, hearing protection devices, or even personal coaches for workouts and training. The future of headphones is still unknown, but their development and innovations will surely continue in the coming years.

Different Types of Headphones

At the present time, shopping for headphones can be quite challenging for many people due to the many options available in the market and even online. Before buying, you need to know which type of headphones are best for you, which are among the most difficult questions to answer. This is because headphones come in different types, and each offers various features. To help you, we’ve also listed in this post the different types of headphones and the features that each of them offers.

1. Over-Ear

black over-ear headphones

Over-ear headphones are also called circumaural headphones. These are the most common types of headphones in the market. They feature earpads that are big enough to fit the whole ear. Compared to other types, over-ear headphones are the biggest in size, and they also have a headband that connects the two earcups.[3] This is a superior style of headphones when it comes to noise reduction as they can make an intimate environment between the listener and the sound they are listening to.

However, over-ear headphones are very capable of noise leakage, which keeps the sound you are listening to in and also allows it in the surrounding environment out. But they are comfortable, especially the higher-end ones, as they do not crunch the ears. On the other hand, they are also the bulkiest.[4]

2. On-Ear

black on-ear headphones

On-ear headphones are also known as supra-aural headphones. They are made the same way as over-ear headphones, but they feature smaller earpads. These earpads rest on the earlobes.[3] Compared to over-ear headphones, these are lighter and create less pressure on the top band that rests on the head. In terms of quality, on-ear headphones can vary greatly, but if you get higher-quality ones, they will deliver on the aspects that you care about the most, such as comfort and sound quality.[4]

3. Earbuds

Earbuds are also known as in-ear headphones. They are the most portable type of headphones as they are small and come in different sizes and shapes. However, earbuds are not just one type. They come in various styles, too. Some of the general advantages of earbuds are portability, lower price, effective noise isolation, and stability while doing other activities. Below are the different types of earbuds:

  • True Wireless Earbuds

a pair of true wireless earbuds

This type of earbuds is popular because they completely lack wires. These earbuds come in a charging case that is easily portable and helps extend their battery life. Also, wireless earbuds sound the same no matter what the source of sound is since all the needed components are built into the housing.

  • Wireless Earbuds

These are the old style of wireless earbuds. They are in-ear headphones that receive audio wirelessly but still have a wire connecting the two earbuds. Their sound quality is on par with the latest true wireless earbuds.

  • Wired Earbuds

wired earbuds

Wired earbuds are still a better-sounding option. They do not depend on DSP for tuning, which makes the sound performance more scalable. They are also the cheapest earbuds in the market.

  • Earphones

wired earphones

The classic earphones sit in front of the ear canal and rest on the earlobes. They do not block the ears and let in more ambient noise. This is a great choice if you want better awareness. They are also comfortable to wear as there is no in-ear pressure. They are lightweight, and you can barely feel them. This is a great choice if you don’t care much about the best sound quality and only want something that you can use to watch videos or listen to music.[3]

4. Bone Conduction Headphones

woman using bone conduction headphones

These are unique headphones that use bone conducting technology to transmit sound through the cheekbones. They essentially bypass the outer ear. This is perfect if you want to listen to sounds without blocking your ears to give you awareness. They are highly stable as they usually sit over the ear. These types of headphones can also help people with hearing problems. The downside of this type of headphones is that the audio lacks bass and detail.[3]

5. Closed-Back Headphones

wireless closed-back headphones

These can be any type of headphones, such as over-ear, on-ear, or in-ear, that have fully closed ear cups. Only closed-back headphones can have suitable sub-bass extensions. This type of headphone can prevent outside noise from sneaking in and ruining the listening experience. The full enclosure that it features traps the sound waves and improves bass response. The only downside is that closed ear cups and a tight seal prevents sufficient air circulation, especially for leather earpads. This can make the skin hot and sweaty.[3]

6. Open-Back Headphones

black open-back headphones

Open-back headphones have semi or fully open earcups. They are usually visible and only protected with a wire mesh. This is the favorite type of headphones by many audiophiles due to their natural sound. It prevents the sound from feeling trapped inside the cups, which results in an airier and more natural presentation. They can also handle higher volumes better with less distortion.[3]

7. Active Noise-Cancelling Headphones

Active noise cancellation is quite a new trend in the world of headphones. These types of headphones can block surrounding noise actively by recording it, inverting its phase, and sending it back to the ears. Both sounds cancel themselves out consequently before reaching the eardrums. These are great for commuters and travelers who wish to reduce annoying engine noises. They can also be used to better concentrate on work or to improve sleep quality.[3]

Most Popular Headphone Brands

In addition to the different types and styles of headphones in the market today, another thing that most buyers consider is the brand. There are hundreds of headphone brands out there from both big and small tech companies. Therefore, there’s a wide selection to choose from if you are thinking of buying one, which can be a bit daunting. But if you are searching for the best headphones that will give you the best listening experience, here are some of the top brands that you might want to look for:

1. Sennheiser

Sennheiser is one of the most recognizable brands among disc jockeys, musicians, recording artists, and even gamers in the industry. It offers many different headphones that are uniquely created for every person’s needs and wants. Sennheiser is also one of the most accessible brands out there. It has been around for over 70 years as a manufacturer of audio equipment, including microphones. It is a German company that was founded by Fritz Sennheiser in 1945.[5]

2. Bose

Bose is known to offer high-end and expensive headphones. It was a corporation that was founded by Amar Bose in 1964. When people are asked about pricey headphones, Bose is one of the first brands to come to their minds. But the brand takes pride in making audiophile-grade music performances. Buying their headphones is an upgrade that no one will find in most headphones in the market. Bose is also popular for its noise-canceling headphones. That’s why it is among the top picks for people who work in aviation and aeronautics.[5]

3. Sony

Sony is the tech giant that made the original Walkman, which made music portable. This explains why it also does not fall far behind when it comes to the best headphone brands in the world. In the world of headphones, Sony is probably the most recognizable brand. It is a Japanese company that was founded in 1946. It offers a wide selection of headphones that people can choose from without hurting their wallets too much. It is one of the household names for sound quality.[5]

4. Beyerdynamic

Another pioneer brand in the headphone market is Beyerdynamic. It is a company that was established in 1942 in Berlin, Germany. It is not as popular as the other brands, but it is highly regarded as the top headphone brand in the world. This brand has made premium and best-sounding headphones for over seven decades. Its headphones are classy and aesthetically designed. They are also comfortable with the large ear cups that they feature. They offer all sorts of headphones, such as in-ear headphones, studio headphones, high-fidelity headphones, and even mobile headphones. [5]

5. AKG

AKG is also a trusted and world-famous headphone brand that is based in Vienna, Austria. It is owned by South Korean electronics giant Samsung. It offers headphones with bulky designs. They are durable and made with high-quality materials. Most of their headphones are used for studio recordings. It is also the company that made the first-ever supra-aural, open-back pair of headphones back in 1959. It offers the best headphones for music enthusiasts.[5]

6. Audio-Technica

Audio-Technica is a brand founded by Hideo Matsushita in 1962. It is a Japanese brand that is award-winning. It has a remarkable track record, and it specializes in Hi-Fi headphones. It also offers budget-friendly headphones, as well as mid-range and high-end models. They make the best-sounding and most comfortable pair of headphones, both for personal and professional use. It is also among the few headphone manufacturers out there that offer wider customization options for their headphones.[5]

7. Shure

Shure is another brand of elite and high-grade headphones. The company was founded in Chicago, Illinois, in 1925 but only ventured into creating over-ear headphones in 2009. This is also a popular headphone brand among audiophiles. It is used by sound engineers and disc jockeys, and as well as music aficionados. Even though their headphones are quite expensive, you are sure of an investment that is worth your money. With this brand, you are truly paying more for that extra quality.[5]

8. Pioneer

Pioneer is a popular brand when it comes to car stereos and home speakers. They also make headphones of excellent quality. The company began making audio equipment around 80 years ago. But it debuted in making headphones in 1960. Later on, it became a Japanese tech firm that is popular across different countries in the world. It offers users distortion-free listening with its headphones. [5]

9. Beats

Beats is one of the most popular headphone brands that was ever created in the world. It is a relatively new brand that was established in 2006 by hip-hop legend and producer Dr. Dre or Jimmy Iovine and his team. The headphones boast excellent audio fidelity with a stylish visual design and solid bass implementation. But many users love it due to its fashionable and attractive look.[5]

10. Panasonic

Panasonic is a popular Japanese brand that was founded in 1918 by Konosuke Matsushita. It is a major rival to Sony. When it comes to headphones, Panasonic may not be that popular, but it offers some of the decent and most-affordable noise-canceling headphones in the market. Its headphones are perfect for casual and everyday use, particularly when commuting.[5]

Headphones By the Numbers

woman testing headphones in a store

Today, almost every one of us uses headphones and earbuds every day. Some use them for work, while others use them for leisure, such as listening to music, watching movies, and more. With this, have you ever thought about how many people in the world use headphones? How much do you think the industry earns? If you have these questions in mind, we’re here to help you answer them. In this part, you will find numerical data and statistics about headphones.

Unit Shipments of Headphones in the World

According to Statista, the global headphone unit shipments have grown significantly from 2013 to 2020. You can check out the graph below:

Unit Shipments of Headphones Worldwide from 2013 to 2020

In 2020 alone, there were 549 million units of headphones shipped worldwide, which is a positive growth in the industry. That is a 14% growth value compared to the previous year.[6]

Headphone Market in the United States

In the United States, the average revenue per capita for the headphones industry in 2018 was $12.03. In 2016, headphones surpassed $13 billion in revenues for the first time, with more than 336 million units sold. The volume sales of headphones have been rising at an average of 12 million each year.[7] You can view the graph below for the size of the headphone market in the United States by product:

Size of the Smart Headphone Market in the United States by Product from 2014 to 2022 (in million US dollars)

According to research, wireless headphones are becoming more common in the industry. Based on the data from The Verge, in 2016, wireless sets were responsible for 14% of the overall market.

Most Used Headphone Brands in the United States

There are indeed many different headphone brands available in the United States today. But most people are into using specific brands of headphones. Check out the graph below to see the most used headphone brands in the United States:

Most Used Headphone Brands in the United States in 2021

According to the Statista Global Consumer Survey that was conducted in the United States in 2021, 31% of the respondents said that they are using “Apple” when asked about the brand of their personal headphones. This was followed by Beats at 15%, Bose at 13%, Sony at 12%, and Samsung at 11%.[8]

Kinds of Headphones Owned in the United States

In addition to headphone brands, most people in the United States are also fond of using certain types of headphones. You can check out the graph below for the types of headphones owned in the United States:

Types of Headphones Owned in the United States

According to Kunst, the statistics above show the types of headphones that were owned by most people in the United States in 2017. Based on a Statista survey, 49% of the respondents said they owned over-ear headphones and earbuds.[9]

Top Headphone Brands in the World

In 2017, the top headphone brands in the world constituted more than 80% of the market share. The global market for the complete list of headphone companies in the world was valued at around $11 billion during that time, and it is forecasted to grow at a CAGR of more than 7% for the next five years to surpass $15 billion by 2022. The growth of the top headphone companies in the world is driven by the growth of the music industries as well as mobile phones. Check out the graph below for the top headphone brands in the world:

Top Headphone Brands in the World by Revenue

According to BizVibe, in 2017, JBL had the top annual revenue among the different headphone brands. It earned an estimate of $20 billion in 2017. It was followed by Philips with $18 billion annual revenue, Bose with $3 billion, Beats with $2 billion, and Sony with $1.5 billion.[10]

15 Interesting Facts About Headphones

yellow headphones

If you are searching for more information about headphones, you can find below some of the most interesting facts about them that might blow your mind.

  1. The very first headphones only had one earpiece that had to be connected to a contraption together with a mouthpiece for transmission.
  2. The first pair of modern headphones were made by Nathaniel Baldwin in his kitchen.
  3. The term “cans” was actually slang that was used in the past for earpieces or for anything that creates sound and had to be listened to by putting them to the ear.
  4. Headphones were really not meant to be portable. Back in the ‘70s, headphones were used for listening to records at home, and they could weigh from 1 to 2 kilograms.
  5. The noise-cancellation technology in the headphones industry was made due to the noisy airplane engine.
  6. The first dynamic headphones were invented by Beyerdynamic, and they are still being produced today.
  7. Earbuds are made popular by the Apple iPod.
  8. Skullcandy introduced wild and vibrant styles of headphones that were designed to be noticed.
  9. The line of celebrity headphones was resurfaced by Beats by Dr. Dre.
  10. Did you know that earpieces fall out on stage all the time? Yes. In fact, it happened to artists like Beyonce, Mariah Carey, Adam Levine, and more.
  11. When testing earbuds, it is better to use older music. It’s because new songs tend to have their frequencies compressed and enhanced to get the loudest possible sounds.
  12. The ones that feature a microphone in them are referred to as headsets.
  13. Wearing headphones and any other earpiece for 2 hours straight can weaken one’s hearing ability and may also increase the growth of the bacteria in the ears.
  14. Low-quality earbuds can make people prone to ear infections.
  15. The very first “truly wireless” in-ear headphones were presented at the IFA technology show that was held in Berlin. It was unveiled by a Japanese consumer electronics manufacturer Onkyo.

Conclusion

For many people, headphones and earbuds are indeed part of their everyday lives. Some people’s day may not be complete without listening to his or her favorite song while commuting to work. Students use them to play some music that can help them focus on their assignments. And, of course, headphones are widely used in recording studios by artists, sound engineers, and editors. With this, we can say that in the coming years, there will be more improvements and developments in headphone technology.

Therefore, we can expect headphone brands to reveal more high-tech headphones and earbuds that will cater to the needs of both professional and casual headphone users out there. We hope this article helped you learn more about headphones.

References

[1] Editor, C. (2021, September 3). When were headphones invented: The complete history. Headphonesty. Retrieved December 7, 2021, from https://www.headphonesty.com/2021/05/when-were-headphones-invented/.

[2] Newman, M. (2017, September 5). The history of headphones: Cool material. Cool Material. Retrieved December 7, 2021, from https://coolmaterial.com/roundup/history-of-headphones/.

[3] Ferjan, M. (2021, August 9). 12 types of headphones (and their Pros & Cons). HeadphonesAddict. Retrieved December 8, 2021, from https://headphonesaddict.com/types-of-headphones/.

[4] Sean. (2021, May 17). Home. The Wire Realm. Retrieved December 8, 2021, from https://www.wirerealm.com/guides/different-headphone-types-list.

[5] Men’s Gear Editors. (2021, September 19). 13 best headphone brands in the world. Men’s Gear. Retrieved December 9, 2021, from https://mensgear.net/best-headphone-brands/.

[6] Vailshery, L. S. (2021, November 22). Global headphone unit shipments 2020. Statista. Retrieved December 10, 2021, from https://www.statista.com/statistics/236075/revenue-of-headphone-shipments-in-the-united-states/.

[7] Gaille, B. (2018, November 12). 23 headphone industry statistics and trends. BrandonGaille.com. Retrieved December 10, 2021, from https://brandongaille.com/23-headphone-industry-statistics-and-trends/.

[8] Kunst, A. (2021, August 24). Headphone usage by brand in the United States 2021. Statista. Retrieved December 10, 2021, from https://www.statista.com/forecasts/997153/headphone-usage-by-brand-in-the-us.

[9] Kunst, A. (2019, September 3). Most popular headphone types in the US 2017. Statista. Retrieved December 10, 2021, from https://www.statista.com/statistics/696905/headphone-types-owned-in-the-us/.

[10] BizVibe Editors. (2019, June 1). Top 10 headphone brands in the world – industry overview. Bizvibe Blog. Retrieved December 10, 2021, from https://blog.bizvibe.com/blog/electronics-and-computers/top-10-headphone-brands-world.

[11] Editor, C. (2021, September 2). 6 things you probably didn’t know about headphones. Headphonesty. Retrieved December 10, 2021, from https://www.headphonesty.com/2016/01/6-things-you-probably-didnt-know-about-headphones/.

[12] VOX Music Player. (2017, August 11). 10 facts about 🎧headphones😉. Medium. Retrieved December 10, 2021, from https://medium.com/@Coppertino/10-facts-about-headphones-9ded48d6e075.