Is the ubiquity of headphones just another emblem of catastrophic social decline, edging us even deeper into narcissism and unsociability? PHOTOGRAPH BY MARTIN PARR / MAGNUM

Anyone who has recently spent time in a public space—traversing the aisle of an airplane, say, lurching toward your seat adjacent to the toilet, trying to shift your backpack without thwapping a fellow traveller on the forehead—has likely noticed the sudden and extraordinary ubiquity of headphones. “Do people really like music this much?” I have wondered, incredulously, while tallying endless white earplugs. The outside world, once a shared auditory environment, has been effectively fractured. We now lilt about in our own bubbles of self-programmed sound.

In 2012, the headphone industry saw a quick thirty-two-per-cent leap in revenue (concurrent with the increasing availability of smartphones and other devices that store and play back audio), and since then the market has only continued to swell. A 2014 survey by the “music lifestyle brand” Sol Republic found that fifty-three per cent of millennials—defined, for the survey’s purposes, as adults between eighteen and thirty-four years old—owned three or more pairs, and wore headphones for nearly four hours every day. Seventy-three per cent admitted to having slid a pair of headphones on to “avoid interaction with other people.” That same year, GQ, in a spread on its Web site, reconfigured headphones as the au-courant ornament for modish men: “The newest fashion accessory isn't a fashion accessory at all. It’s head-swaddling, high-style headphones that make as much of a statement as anything else you’re wearing,” the copy read.

Certainly, headphones are an obvious method of exercising autonomy, control—choosing what you’ll hear and when, rather than gamely enduring whatever the environment might inflict upon you. In that way, they are defensive; users insist upon privacy (you can’t hear what I hear, and I can’t hear you) in otherwise lawless and unpredictable spaces. Should we think of headphones, then, as just another emblem of catastrophic social decline, a tool that edges us even deeper into narcissism, solipsism, vast unsociability? Another signifier of that most plainly American ideology: independence at any cost?

It turns out that observers have been fretting about headphones—and the disconnection they facilitate—for decades. Early Walkman prototypes included a second headphone jack so you could share your tunes with a buddy; Sony C.E.O. Akio Morita later admitted that he “thought it would be considered rude for one person to be listening to his music in isolation.” In 1981, just two years after the Walkman was introduced to the U.S. market (at two hundred dollars, it was an upper-middle-class indulgence), a Times writer described the view on the streets: “Suddenly, waves of people were walking about with little foam-rubber circles on their ears and expressions of transport on their faces in a scene that was almost Orwellian.” Another story, from 1980, described a man having to sell his Walkman to save his marriage: “ ‘My wife insisted that I was tuning her out for reggae,’ he said sadly.” In 1999, in an article commemorating the Walkman’s twentieth anniversary, the reporter Phil Patton wrote, “The Walkman and its rivals quickly became a landmark in the history of media and a symbol of an inwardly focused era.”

Read enough archived editorials, and you begin to believe that as long as human beings have wandered the Earth’s surface, reluctantly grunting at each other about the weather, we have also been entrenched in “an inwardly focused era.” Portable audio, then, is likely more a reflection than an engine of our egotism. The sociologist Edward Hall, in his book “The Hidden Dimension,” from 1966, introduced the discipline of proxemics, which he defined as “the interrelated observations and theories of man’s use of space as a specialized elaboration of culture.” Hall is responsible for the notion of so-called personal space, or the invisible force field most Americans ensconce themselves in while moving through public places; a breach of implied boundaries (per Hall, the human ego extends about a foot and a half outside the body) is neither welcome nor tolerated. No indiscriminate or uninvited contact, the social contract goes. Certainly never any uncomfortably close talking! As W. H. Auden wrote in his poem “Prologue: The Birth of Architecture,” “Some thirty inches from my nose / The frontier of my person goes.” Headphones help demarcate personal space. They allow us to feel cloistered, safe, and comfortably alone.

One of the more interesting revelations included in the Sol Republic survey is the news that empowerment anthems—like Survivor’s “Eye of the Tiger,” Katy Perry’s “Roar,” Kanye West’s “Stronger,” and (no joke) the “Chariots of Fire” theme—are especially popular among headphone devotees. People like to stomp around to jams that instantly position them as scrappy and determined underdogs, overcoming tremendous odds. (The original music video for “Eye of the Tiger” features the members of Survivor marching down the street in combat formation, their collective gaze unblinking, their strides assured; it turns out they’re simply walking to band practice in a garage.) These days, people seem to be perpetually gearing themselves up for the epic battle of merely existing. At the end of the day, jogging up to our front doors, we are all Rocky, reaching the summit, conquering that last step: “Just a man / and his will / to survive!” We rip our headphones off, triumphantly. We did it! Another day closer to death!

As more and more people choose to listen to music on headphones—and we are now nearly forty years deep into portable audio; I have a friend who claims he only listens to music on headphones—it seems silly not to wonder how that technology might be beginning to dictate content. If headphones allow for more introspection, do headphone users favor introspective sounds? If there’s been a thematic through line in the past several years of pop music, it’s been messages of self-reliance and liberation, songs that place us at the center of our own heroic arcs. Obviously, that’s hardly new terrain for pop, but I’d argue that it has reached a noticeable apex this decade. Are headphones partially responsible for the shift?

I wondered, too, about writers like Kanye West and Drake, two of the most critically and commercially successful rappers of our time, both prone to bald confessionalism. Drake’s album “Views,” released earlier this year, is fat with hyper-emotional asides. “Why you gotta fight with me at Cheesecake? / You know I love to go there,” he pleads in “Child’s Play.” Drake is not an un-self-aware figure—when he refers to enjoying a meal at the Cheesecake Factory, he is doing so with deep knowledge of his audience, and of what they find funny, and of what they find real—but a lyric like that is still revelatory, intimate, pure. It is precisely the kind of embarrassing thing we shout at the people closest to us right when we are at our most vulnerable; it is a sentiment intended for an audience of one.

Regardless of whether that intimacy is performative, it is, at the very least, magnified by the cocoon of headphones. In that moment, it’s you and Drake, alone—telling secrets, admitting frailty. “You know I love to go there.”

When I asked the Grammy-winning record producer Bob Power—who produced Erykah Badu’s “On and On” and D’Angelo’s “Brown Sugar,” and recorded A Tribe Called Quest’s first three albums—how hearing music through headphones technically varies from hearing it on an in-room stereo of some sort, he pointed out three differences (though all playback systems, he acknowledged, have their own sonic anomalies). The first is a heightened sense of the stereo field, as the left and right signals aren’t as intermingled as they would be via speakers connected to a receiver. (Some audiophiles will argue for the superiority—the more coherent feel—of mono sound, in which the channels aren’t separated out at all.) The second has to do with how extreme frequencies are rendered: “Because the bass and treble areas are hard to reproduce accurately, factory earbuds will often sound harsh, emphasizing the mid-range and upper mid-range. This is not necessarily because they are actively boosting the signal in those areas; it’s often because they are not handling the rest of the signal—the highs and lows—very well,” he explained. Finally—and most important—he noted “a sense of being closer to the music, usually referred to as presence. Even if the track has a lot of ambience, it will appear closer to the listener—[it’s] literally right in their ear.”