I worried about ringing the doorbell. Then I noticed two ragged rectangles of dried, blackened adhesive on the door frame, one just above and one just below the button. I deduced that the button had been taped over at some point but was now safe to use. I pressed as gently as I could, and, when the door opened, I was greeted by a couple in their early sixties and their son. The son has asked me to identify him only as Mark, his middle name. He’s thirty years old, and tall and trim. On the day I visited, he was wearing a maroon plaid shirt, a blue baseball cap, and the kind of sound-deadening earmuffs you might use at a shooting range.

Mark and I sat at opposite ends of a long coffee table, in the living room, and his parents sat on the couch. He took off his earmuffs but didn’t put them away. “I was living in California and working in a noisy restaurant,” he said. “Somebody would drop a plate or do something loud, and I would have a flash of ear pain. I would just kind of think to myself, Wow, that hurt—why was nobody else bothered by that?” Then everything suddenly got much worse. Quiet sounds seemed loud to him, and loud sounds were unendurable. Discomfort from a single incident could last for days. He quit his job and moved back in with his parents. On his flight home, he leaned all the way forward in his seat and covered his ears with his hands.

That was five years ago. Mark’s condition is called hyperacusis. It can be caused by overexposure to loud sounds, although no one knows why some people are more susceptible than others. There is no known cure. Before the onset of his symptoms, Mark lived a life that was noise-filled but similar to those of millions of his contemporaries: garage band, earbuds, crowded bars, concerts. The pain feels like “raw inflammation,” he said, and is accompanied by pressure on his ears and his temples, by tension in the back of his head, and, occasionally, by an especially disturbing form of tinnitus: “You and I would have a conversation, and then after you’d left I’d go upstairs and some phrase you had been saying would repeat over and over in my ear, almost like a song when they have the reverb going.” He manages his condition better than he did five years ago, but he still lives with his parents and doesn’t have a job. The day before my visit, he had winced when his father crumpled a plastic cookie package that he was putting in the recycling bin. By the end of our conversation, which lasted a little more than an hour, he had put his earmuffs back on.

Hyperacusis is relatively rare, and Mark’s case is severe, but hearing damage and other problems caused by excessively loud sound are increasingly common worldwide. Ears evolved in an acoustic environment that was nothing like the one we live in today. Daniel Fink—a retired California internist, whose own, milder hyperacusis began in a noisy restaurant on New Year’s Eve, 2007, and who is now an anti-noise activist—told me, “Until the industrial revolution, urban dwellers’ sleep was disturbed mostly by the early calls of roosters from back-yard chicken coops or nearby farms.” The first serious sufferers of occupational hearing loss were probably workers who pounded on metal: blacksmiths, church-bell ringers, the people who built the boilers that powered the steam engines that created the modern world. (Audiologists used to refer to a particular high-frequency hearing-loss pattern as a “boilermaker’s notch.”)

Today, the sound source that people first think of when they think of hearing loss is amplified music, the appeal of which may be biological. In 1999, two scientists at the University of Manchester, in England, conducted an experiment in which they had students listen to songs at dance-club volumes, which are high enough to cause permanent damage if the exposures are long enough. The scientists concluded that the loud music stimulated the parts of the subjects’ inner ears that govern balance and spatial orientation, thereby creating “pleasurable sensations of self-motion”: crank up the volume, and you feel as though you’re dancing when you’re sitting in your seat. Classical musicians and their audiences face risks as well. For the musicians, the threat comes not just from their own instrument (violinists, like right-handed infantrymen, tend to lose hearing on their left side first) but also, often more significant, from the instruments of the musicians who sit behind them.

Watch “The Backstory”: David Owen reports on noise pollution and our increasing understanding of its serious impact on human health and on wildlife.

Modern sound-related health threats extend far beyond music, and they affect more than hearing. Studies have shown that people who live or work in loud environments are particularly susceptible to many alarming problems, including heart disease, high blood pressure, low birth weight, and all the physical, cognitive, and emotional issues that arise from being too distracted to focus on complex tasks and from never getting enough sleep. And the noise that we produce doesn’t harm only us. Scientists have begun to document the effects of human-generated sound on non-humans—effects that can be as devastating as those of more tangible forms of ecological desecration. Les Blomberg, the founder and executive director of the Noise Pollution Clearinghouse, based in Montpelier, Vermont, told me, “What we’re doing to our soundscape is littering it. It’s aural litter—acoustical litter—and, if you could see what you hear, it would look like piles and piles of McDonald’s wrappers, just thrown out the window as we go driving down the road.”

In February, Bruitparif, a nonprofit organization that monitors environmental-noise levels in metropolitan Paris, published a report that combined medical projections from the World Health Organization with “noise maps” based partly on data from its own network of acoustic sensors. It concluded, among many other things, that an average resident of any of the loudest parts of the Île-de-France—which includes Paris and its surrounding suburbs—loses “more than three healthy life-years,” in the course of a lifetime, to some combination of ailments caused or exacerbated by the din of cars, trucks, airplanes, and trains. These health effects, according to guidelines published by the W.H.O.’s European regional office last year, include tinnitus, sleep disturbance, ischemic heart disease, obesity, diabetes, adverse birth outcomes, and cognitive impairment in children. In Western Europe, the guidelines say, traffic noise results in an annual loss of “at least one million healthy years of life.”