The inaugural breakthrough in the field of hearing restoration occurred in the late nineteen-eighties, when two researchers discovered, independently, that the ears of young chickens do something that human ears don’t: they rapidly regrow dead hair cells, restoring lost hearing within weeks. No mammal is known to share that enviable capability, but self-healing hair cells look enough like non-self-healing hair cells that scientists have been tantalized ever since by the possibility that human ears might be induced to repair themselves, too. In 2011, the Hearing Health Foundation, based in New York, created the Hearing Restoration Project, a consortium of fourteen scientists who agreed to work together toward that goal, partly with funding from the foundation. One of the originators of the project, Edwin Rubel, who was a co-discoverer of hair-cell regrowth in chickens, told me, “It’s potentially the best thing that ever happened, because it really does bring together a lot of different kinds of expertise.”
Four years ago, Albert Edge—a member of the consortium and a researcher at the Eaton-Peabody Laboratories, part of Massachusetts Eye and Ear—led a group of scientists who showed that young mice with noise-damaged ears could regenerate hair cells and recover some hearing if a drug was delivered into their inner ears shortly after they were deafened. It was the first time that mammals had proved able to regenerate hair cells. The drug, which had been developed for treating Alzheimer’s but turned out to be unsuitable for that, suppresses the activity of a protein that prevents hair cells from being created by so-called supporting cells—cells in the cochlea that function something like stem cells. “What that shows, beautifully, is that there is something there that can support regeneration,” Rubel said. “We just have to figure out how to goose it along.”
I visited Edge’s lab not long ago. A postdoctoral fellow there told me that she and her colleagues were currently able to improve the hearing of a deafened mouse by about fifteen decibels. “Which is good,” she said, “but we’d like to improve it further.” She took me up a flight of stairs to a small room containing a piece of equipment about the size of a washing machine. “This is the chamber we use to deliver high levels of noise, to kill off hair cells,” she said. On a black-and-white video monitor, I could see that the chamber contained a small cage with several mice inside. The mice appeared to be running around normally, but they were being subjected to two hours of steady noise at above a hundred decibels—enough to ruin their hearing, like being in a front-row seat at a Metallica concert.
Recently, Edge and several other researchers succeeded in causing supporting cells they’d extracted from normal mice to divide and differentiate into large clusters of hair cells. At the lab, Danielle Lenz, a co-author of the paper describing that experiment, put on latex gloves, washed her hands with alcohol, and removed two plastic trays from a shelf in an incubator, then placed them under a microscope. “In the second tray,” she said, “you can clearly see the organoids that have been formed from the single cells in the first tray, and you can see that they are multicellular.” The benefit right now is in the laboratory—having access to a big supply of living hair cells in dishes makes screening potential remedies easier—but there are hopes for bigger things. Edge told me, “The ear is maybe a little bit behind the eye, in terms of treatment, but there has been a lot of progress, and between the soldiers and the baby boomers there’s a lot of interest.”
Eaton-Peabody’s director is Charles Liberman, whose office is down the hall from the mouse-deafening chamber. In a major study a decade ago, he and his colleague Sharon Kujawa solved a mystery that had puzzled some audiologists for years: the fact that two people with identical results on a standard hearing test, called an audiogram, could have markedly different abilities to understand speech, especially against a background of noise. The reason, they discovered, has to do with nerve connections. Scientists had known for a long time that most hearing impairment involves damage to the synapses and nerve fibres to which hair cells are attached, but they had assumed that the nerve damage followed hair-cell loss, and was a consequence of it. “What we discovered is that it’s actually the connections between the sensory cells and the nerve fibres that go first,” Liberman told me. “They are much more vulnerable than the sensory cells.” The hearing of a person who has trouble understanding speech can appear normal or nearly normal on an audiogram, because a standard hearing test measures only the ability to detect pure tones along a scale of frequencies. It requires only functioning hair cells, Liberman said, and is unaffected by nerve damage until more than eighty per cent of the synapses are gone. For that reason, the phenomenon he and Kujawa explained is now usually referred to as “hidden hearing loss.”
A disturbing implication of their finding is that hearing can be damaged at decibel levels and exposure times that have traditionally been considered safe. Nonetheless, among researchers, the discovery has been a cause for optimism, because reconnecting nerve synapses is almost certain to be easier than regenerating functioning hair cells inside human ears. “This is the simplest sensory circuit that you could possibly have,” Liberman said. “It’s one sensory cell type and one neuronal cell type, and it’s possible to do local delivery through the eardrum.” He and others have successfully restored some damaged connections in lab animals, and he believes that far greater advances are to come. “In the past five years, there’s been an explosion of biotech companies getting serious about the inner ear for the first time,” he continued. “I think most people in the field would say it’s no longer a question of if we will be able to unlock enough of the secrets but merely a question of when.”
If I could relive my adolescence, I wouldn’t listen to Steppenwolf with loudspeakers leaning against my head, and I wouldn’t have cherry-bomb fights with my friends unless I was wearing ear protection. On the recommendation of James Henry, at the V.A., I now own several sets of so-called musician’s earplugs, which reduce the over-all level of sound but maintain the full sonic spectrum—unlike regular foam earplugs, which disproportionately mute high frequencies. I wear them even while vacuuming (or will the next time I vacuum anything), and if I were a hunter I would buy a pair of microprocessor-controlled earmuffs, which amplify quiet sounds but turn gunshots into muffled pops.
Luckily for those of us who have been careless with our ears, there are hearing aids. Most of them are made by six major manufacturers, only one of which is based in the United States: Starkey Hearing Technologies, whose headquarters are in Eden Prairie, Minnesota. Starkey’s greatest marketing triumph occurred in 1983, when President Ronald Reagan revealed that he was wearing one of its products. (The main source of Reagan’s hearing problem was a gun that someone fired near his right ear on a movie set in the early thirties.)
I visited Starkey in February, and when I arrived at the company’s testing department the receptionist greeted me in a voice that she seemed to have turned up a couple of notches—an occupational necessity, I assumed. Another employee told me, as I waited to be examined by an audiologist, that I had been preceded recently by two members of a well-known rock band that’s been around since the early seventies. The rockers, she said, looked “very old and very weathered,” and had hearing problems they’d apparently ignored for decades. “Oh, my gosh, they’ve lived hard,” she said. But they have hearing aids at last.
Before my ears were tested, a technician used a digital otoscope and a curette—a long, wirelike tool with a tiny scoop at the end—to remove wax from my external auditory canals, while I watched on a video monitor that magnified everything forty times. The wax pieces look like boulders made of amber. The technician pointed out several bumps, which he said were exostoses, benign bone growths that form in response to repeated exposure to cold water and are common among surfers (who refer to the condition as “surfer’s ear”). Large exostoses can cause hearing loss, by blocking the auditory canal. “But yours are too small to worry about,” the technician said.
Then I sat in an insulated booth and pressed a button every time I heard a tone. An audiologist outside the booth plotted the results on an audiogram, and showed me that, while most of my hearing falls within the lower half of the normal range, I have a mild loss in both ears above four thousand hertz, which is about the frequency of the highest C on a piano—a typical result for a non-rocker in his early sixties. As sounds at those frequencies fade, speech becomes harder to understand, because consonants are pitched higher than vowels and when they disappear sentences turn to mush. Struggling to make out what other people are saying leaves less brain power for anything else. A Starkey research scientist told me that, as people lose hearing, they rely more on unconscious lipreading, which even in people with good hearing accounts for as much as twenty per cent of comprehension. To demonstrate, he covered his mouth. “If you can’t get those visual clues,” he said, “listening becomes more challenging and more effortful, even for something like this.”
Based on my audiogram, I was fitted for a pair of Starkey’s Muse hearing aids. Each unit sits behind an ear, as my grandmother’s hearing aid did, but is so small that it’s all but invisible. A coated wire leads to a receiver—red for right, blue for left. Each receiver is about half an inch long and the diameter of a kitchen match, and it goes right into the ear canal. A button on the part behind the ear allows me to choose among settings programmed by the audiologist. Two of them add a subtle tone that’s meant to mask my tinnitus, which during my hearing test she pinpointed at about six thousand hertz. My main reaction when I first put the hearing aids on was mild annoyance at the sound of my voice. I also became more aware of turning pages, creaking doors, and the surprisingly varied noises made by my pants. The audiologist said that people with new hearing aids get used to all that within about a month, as the brain adjusts.
With my hearing aids on, I was given a tour of the premises. Hearing aids that fit snugly into the ear canal, as many do, are custom-made from silicone impressions that audiologists create by injecting goop into patients’ ears. The cured impressions look like miniature Henry Moore sculptures. Laser scanners turn them into three-dimensional digital files, and the images are trimmed, shaped, and manipulated by technicians using an in-house computer program that’s essentially Photoshop for ear canals. I saw test hearing aids being subjected to stresses that were meant to replicate the surprisingly hostile microenvironment of an external auditory canal: baking in an oven suffused with “salt fog”; lengthy exposure to blowing clouds of dustlike talc; submersion for days at the bottom of a metre-tall column of water.
The Starkey line with the most features is Halo, the first version of which was introduced in 2014. Halo wearers can stream music, phone calls, recorded books, television shows, and other audio content via Bluetooth directly into their hearing aids from all current Apple devices. The hearing aids adjust automatically to different environments. They eliminate wind noise and reduce background sounds between spoken syllables during conversations in crowded places, and they can be used with a smartphone app that enables them to do things like switch to a customized automobile mode as soon as the phone’s accelerometer detects that the wearer is moving faster than ten miles an hour. Chris McCormick, who is Starkey’s chief marketing officer, told me, “If you regularly visit a Starbucks, you can fine-tune a setting for that particular environment—the barista grinding coffee beans, other customers talking—and then geotag it, so that when you pull into the parking lot your hearing aids will switch to that mode.”
Successfully linking hearing aids and iPhones required a long collaboration between Starkey and Apple. One challenge was that hearing aids, because of their size, have to operate on minuscule voltages, much lower than the ones that smartphones use. Another was that the human body acts like a sponge for many radio frequencies, blocking communication between the device in your left ear and the phone in your right pocket. In Starkey’s main research building, I stepped into a chamber that from the outside looked like a walk-in freezer. Mounted on a pedestal and surrounded by a ring of sensors was a plastic head, with ears. “It contains a gel that mimics the frequency-absorption characteristics of a human head,” a scientist said. A technician outside the chamber had been bombarding it with radio waves and studying the results on four large color monitors.
Starkey’s newest hearing aid, the SoundLens Synergy, is even smaller than Halo and Muse—too small for Bluetooth. Each unit looks scarcely larger than the aspirin-size battery it runs on, and is designed to be inserted deep into an ear canal. Chris McCormick pushed one into his own ear, and turned his head to the side; I could see no part of it, even from close up. He retrieved it by pulling on a snippet of nylon filament.
In 2013, Charlie Rose devoted a program to hearing loss, and during the broadcast two of the participants—Eric Kandel, a scientist who won a Nobel Prize in 2000, and Rose himself—were wearing hearing aids. (David Corey, the Harvard Medical School professor I met with, appeared on the program as well, and got a good look.) Yet neither man mentioned that fact, even though the program lasted nearly an hour and hearing aids were a major topic of discussion. The wearing of hearing aids has long been stigmatized in a way that the wearing of eyeglasses has not, and, as a consequence, hearing-aid manufacturers have invested heavily in inconspicuousness—one of several reasons that hearing aids like Halo and SoundLens sell for more than three thousand dollars each.
Attitudes about visibility may be changing, though, now that people of all ages walk around with electronic gadgets sticking out of their ears. Hearing-aid companies increasingly compete with manufacturers of over-the-counter devices known as “personal sound-amplification products.” The cheapest psaps, some of which sell for less than fifty dollars, are notoriously junky and may even exacerbate hearing loss by indiscriminately amplifying harmful sounds. But some companies make user-adjustable Bluetooth devices that have received favorable reviews from technology critics and people with mild hearing problems.
A couple of weeks ago, I had lunch with Kevin Franck, an audiologist at Bose, the sound-equipment company. Snow had fallen overnight, and the restaurant I’d picked, near my home, in Connecticut, wasn’t as crowded and loud as it usually is. “That’s too bad,” Franck said, as we were seated. He was on his way to New York, and had made a detour to show me a new Bose product, still in limited release, called Hearphones—high-fidelity headphones designed, in part, to help people cope with conversations in places like noisy restaurants.
In comparison with SoundLens hearing aids, Hearphones look like a technological throwback: a pair of acorn-size earpieces connected by wires to a choker-like yoke (which can be concealed under a shirt collar). But because Hearphones aren’t meant to be invisible they have room for a long antenna, a big rechargeable battery, high-quality microphones and speakers, and far more power-hungry sound-processing and noise-cancelling technology than could be concealed inside an ear canal.
I put them on. “One of the things you get really good at when demonstrating this device is talking without saying much,” Franck said, then chatted away. I used a smartphone app to raise and lower background sound levels. I could also focus specifically on Franck’s voice or widen the range to include, first, the tables on either side of ours, then some chefs and waiters moving around in the kitchen, behind me. If my cell phone had rung, directional microphones inside the earpieces would have aimed themselves toward my mouth when I answered it. Once I’d found a sound level I liked, I used a slider in the app to fine-tune the pitch. I was able to play music in the background as we conversed—with far better fidelity than is possible with even the most expensive hearing aids—and I could raise and lower its volume independently from everything else.
You wouldn’t wear Hearphones on a first date, probably. But, if I’d had a pair at that noisy restaurant I went to in Dallas, I’d have been able to hear everyone at the table without cupping my ears, and, during the boring bits, to tune out the entire room and listen in peace to my audiobook of “A Game of Thrones.” ♦