The Future of Hearing
How Technologies are evolving to treat and prevent hearing loss.

By  ROBERT EBISCH

The music coming from Bob Dylan and his band at the indoor concert is awesome, but what I can hear of his vocals suggests that people backstage are strangling frogs.

Sure, Dylan’s voice is throaty and growly, but he can articulate his songs as well as anyone. I know it from his CDs. At a distance of more than 50 yards from the stage, however, the form of his words, especially the higher frequencies of his consonants, are lost in the hurricane of sound from the mighty speakers and the reverberations of the theater’s vast interior.

If I were a hearing-impaired person, I might switch my hearing aid to the “T” setting and get the best of Bob with sound of near-studio/CD quality, while the hearing-normal folks around me were still worrying about those frogs and ducks.

At least I could do that if the concert were taking place at Town Hall in Manhattan. It is among the growing number of facilities equipped with “induction loop systems” that broadcast directly from the output of instruments and microphones to hearing aids equipped to receive them.

Science is ringing in a new era in the world of the hearing-impaired, and the technologies to accommodate, treat and prevent hearing loss – and even cure it – are advancing at almost sonic speed. And that’s welcome news, considering how doctors are wringing their hands over study after study predicting hearing loss for a generation that seems constantly connected, almost from birth, to MP3 players.

Age is the major cause of hearing loss, and your level of predisposition to it is genetic. If your parents lost hearing with age, it’s likely you will too. Age-related hearing loss is found in about one-third of people over 60 and half of people over 80. That hearing loss comes from breakdown of the “hair cells” in the cochlea (the spiral-shaped part of the inner ear containing the auditory nerve endings). There are some 16,000-20,000 of them in each ear, and each hair cell is believed to have about 100 tiny hairs known as stereocilia. Sound causes pressure variations in the cochlea, which makes the stereocilia vibrate and send impulses to the brain.

First lost with a combination of age and excessive sound – like loud music from an iPod – are the hair cells that resonate to higher frequencies, which is why speech becomes harder to understand as the ability to hear the higher frequencies of consonants disintegrates. But that could change, thanks to research at the House Ear Institute in Los Angeles.

“We’re developing totally implantable hearing aids, so we may some day implant a device allowing a person to hear without having an [external] aid,” says John House, the institute’s president. Within five years, such hearing aids should be sufficiently developed that the institute will be implanting them in children on a regular basis, House says.

Among other projects at the House Ear Institute are hearing aids that completely bypass the ear and wire sound directly into the brain.

Founded in 1946 by House’s father, Dr. Howard P. House, to advance hearing science and improve the quality of life, the institute is among the world’s leading centers of hearing-related research and education. Besides surgical and other medical interventions, the Institute also does research and development on hearing technologies, such as signal processing algorithms applicable in hearing aids. Hybrid electrical/mechanical hearing aids are another example: The cochlea is implanted with an electrode for high frequencies associated with subtle voice recognition, while standard hearing aids provide the lower frequencies.

“We’ve been working on that for the past five years, and it’s still investigational,” says House. “Maybe within five years, we’ll be able to implant hybrid [hearing aids] in people who have residual hearing but not enough to understand speech.”

The hearing aids of today are digital, with increasingly powerful microchips and software that can customize to the individual’s frequency spectrum of hearing loss and can adjust to the conditions of a noisy gymnasium or a quiet garden. Hearing aids are moving toward unprecedented abilities to convey subtleties like footsteps in another room, the sound of the wind, the nuances in music or the voices of loved ones.

“Analog tends to amplify everything, whereas with digital we can actually tune it to respond only to whatever frequencies are needed, and we can insert different programs so the hearing aid can respond to different sounds,” House says. “There have been tremendous advances in hearing aids in the last five years.”

One example, House says, is that of multiple-microphone hearing aids available just in the last two or three years, which help filter out background noise and tune in on close-up speech. The newest, he says, is the “open fit” hearing aid. It uses a narrow and inconspicuous tube to carry amplified higher frequencies into the ear, leaving the ear largely open to a natural inflow of the lower frequencies without completely plugging the ear like the traditional ear mold.

“In the past, hearing aids couldn’t do that because they couldn’t eliminate the squeal, the feedback problem,” House says. Tiny computers, capable of screening out noise and amplifying pertinent sounds, prevent those problems. “I get very excited about it because it fills a niche that’s been very difficult to fill,” House says. “People don’t like the ear to be completely plugged up. They like to hear their own voice.”

Despite the resounding success of all these technologies and techniques, however, many of them may, in decades to come, become as irrelevant as VHS tape.

“We won’t have a need for some of these technologies, because we’ll be able to regenerate the cochlear hair cells that allow us to hear,” House predicts. “One of the major projects here is related to finding the genes responsible for age-related hearing loss. As we identify those genes, we hope some day we will be able to manipulate those genes and do gene therapy, and not only treat hearing loss but prevent it.”

“Some animals – chickens and fish and frogs – can regenerate their hair cells,” House says. “In humans, or any mammal, they don’t grow back. Now we have been somewhat successful in regrowing hair cells in rats. That’s a long way from humans, but we’re beginning to find out what the key is to turn it back on again.”

Small wonder that House is able to envision reducing the one-third of people who develop significant hearing loss by age 60 to possibly 5 percent within the next 20 years. And beyond that time, House foresees the problems of hearing loss receding still further with advances in areas including hearing-aid technology, surgical reconstruction and prostheses. Once scientists begin to understand how we hear on molecular and cellular levels, hearing loss may become an unheard-of anachronism.