Tom Maholchic, 27, sits in his home in Milton, Mass. Tom suffers from hyperacusis, which in his case, causes everyday sound to be greatly amplified and feel painful.

A jovial laugh, to Tom Maholchic, feels like a knife stabbing his eardrums. So do all sorts of routine sounds — the sizzle of bacon, the ring of a phone, the rush of running water.

“I feel like I have a year-round sunburn deep inside my ears,” said Maholchic, 27.

Researchers have known for years about a condition called hyperacusis, where ordinary sounds seem uncomfortably loud. But they’re just starting to understand that some patients experience a more severe form, where noise is not just heard — but is actually felt, as physical pain.

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Using new lab tools and techniques, pioneering scientists have identified what appear to be pain fibers in the inner ear, or cochlea. They are coining new terms, including “noxacusis” and “auditory nociception,” for this newly recognized sensation of noise-induced ear pain.

The new diagnosis will be an important topic next week at the annual meeting of the Association for Research in Otolaryngology in San Diego, where a three-hour symposium will introduce the research and explain its implications. While some patients with the condition do improve, others risk a setback every time they hear even a moderate noise.

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“People’s lives have been radically altered by the crippling pain that comes with this type of rare noise injury,” said Bryan Pollard, president of Hyperacusis Research, a nonprofit.

“The pain lingers long after the sound is gone, much as the pain from a flesh wound would.” M. Charles Liberman, Harvard Medical School

Patients’ descriptions of the pain are remarkably similar: A sound is usually perceived as the sharp jab of a knife or skewer. The sensation persists as a searing, burning ear pain, often combined with the pressure known as aural fullness and the ringing known as tinnitus.

Maholchic often spends time in this room, so he can look outside the window and feel the sun, since he cannot tolerate going outside during the day. He says that he spends most of his time reading and painting. Kayana Szymczak for STAT

“What even most auditory scientists don’t understand about hyperacusis with pain is that the pain lingers long after the sound is gone, much as the pain from a flesh wound would,” said M. Charles Liberman, a professor of otology at Harvard Medical School and director of a hearing research lab at the Massachusetts Eye & Ear Infirmary.

The problems start with the pea-sized cochlea, a tiny sensory organ buried within a skull bone. It’s tough to reach and impossible to biopsy, thereby hampering experimental work. Within the cochlea, one kind of nerve fiber has long puzzled scientists. These mystery fibers resemble pain fibers elsewhere in the body.

It took 15 years, but using several strains of deaf mice, Jaime García-Añoveros, an associate professor of anesthesiology at Northwestern University Feinberg School of Medicine, found that intense noise causes activity in these fibers. That research, coauthored by Liberman, was published last March in Current Biology.

At around the same time, a lab at Johns Hopkins University found that when certain sensory cells of the cochlea are damaged, as might occur during very loud noise, they release a chemical that activates the mysterious pain fibers. In some people, these fibers seem to switch on — and never switch off.

Noise loud enough to cause immediate pain — like a gunshot or a firecracker going off at close range — is so rare that few people ever experience it, except those in the military.

But exposure over time to more modest noise — from music, movies, sirens, lawnmowers, and a thousand other everyday things — can damage hearing and set off the pain fibers.

Indeed, noise can cause damage even if it doesn’t feel uncomfortably loud in the moment. “Young people don’t report a rock concert as a painful experience,” said Paul Fuchs, a professor of otolaryngology at the Johns Hopkins University School of Medicine, whose research was published in the journal PNAS in November.

Individual susceptibility to noise exposure varies greatly, and may be genetic. There’s no firm estimate of how many people may suffer from noise injury.

Maholchic’s collection of noise reduction earmuffs. Kayana Szymczak for STAT

Few doctors or audiologists are even aware of the condition, though the new findings may encourage them to take patients who complain of ear pain more seriously. “It is time for pain hyperacusis to be recognized as a real symptom, not as a psychosomatic phenomenon,” García-Añoveros said. “This is, in a way, a new sensory modality — a hybrid of pain and hearing.”

For Maholchic, the pain came on abruptly and quite unexpectedly. He never thought his noise exposure was at all unusual. At his student job at the University of Massachusetts, he listened to music on his iPod while he vacuumed. He played in a garage band. Later, he worked at a loud, lively restaurant.

His only symptoms were ear fatigue after band practice and bursts of discomfort from clanking dishes at the restaurant. These warning signs, seemingly inconsequential, quickly resolved.

One night two years ago, however, his ears started ringing. Within weeks, “barking dogs, crowded places, and pretty much any noise considered remotely loud sent shockwaves through my head,” he said in an interview conducted by email, since he must limit his time on the phone.

Maholchic had been living in California, but moved back in with his parents in suburban Boston because the pain was so debilitating. To cushion him from noise, the house has soundproof windows and plenty of carpeting. Maholchic also sometimes wears earplugs or protective earmuffs. And he rations his time spent in potentially painful settings. “If I manage my noise exposure well, I can handle noise better,” he said.

Maholchic has improved enough to be able to take occasional late-night walks while his neighborhood sleeps. But just one surprise noise, like a honking horn, erodes his progress.

“The louder the noise, the greater the impact,” he said. “It angers me to think about all the unnecessary noise I exposed myself to. I was unaware of the harm it could cause.”