Never before have there been so many devices to help the hearing disabled - an estimated half a billion people. Yet only about 15 percent of those in developed countries who need hearing aids actually use them. The reasons include embarrassment, unwillingness to admit a disability, the expense, and the fact that hearing even with the devices isn't perfect. Now Jerusalem's Shaare Zedek Medical Center is offering something new to the middle aged and elderly who have hearing loss. Called Vibrant Soundbridge (produced by the Vibrant Med-El company in Innsbruck, Austria), it is a semi-implantable hearing system for those suffering from mild to severe sensory-neural hearing loss and can't benefit from conventional hearing aids. So far about 2,000 of the devices - approved by the US Food and Drug Administration - are in use in the US and Europe, but Shaare Zedek remains the only Israeli - and Middle Eastern -hospital to do this surgery. Dr. Jean-Yves Sichel, head of its ear, nose, throat, head and neck surgery department, and Dr. Ronen Perez, director of the otology unit, teamed up to do two implants in the past half year, while a few more are being planned. SICHEL, WHO was born near Paris, studied medicine in France and came on aliya with his family in 1989, went immediately to the Hadassah University Medical Center in Jerusalem's Ein Kerem and remained there for 15 years. When Shaare Zedek issued a tender for the head of the ENT department, he applied and was selected. Perez, a graduate of the Hebrew University-Hadassah Medical School, went on a fellowship at the University of Toronto and has been at Shaare Zedek since 1994. THE IDEA of putting a vibrator on one of little bones in the middle ear began in Japan over 30 years ago. The semi-implanted hearing aid was finally invented by a man named Geoff Ball, who had hearing problems himself. Med-El purchased rights to the invention, and has been manufacturing it for 10 years, since the first one was implanted. Although part of it is inside the head, it is not a cochlear implant - a surgically implanted electronic device that provides a sense of sound to a person who is profoundly deaf. The cochlear implant is often referred to as a "bionic ear" that - unlike hearing aids - does not amplify sound. Instead, this implant, used by many hundreds of Israeli children and now adults as well, works by electrically stimulating any functioning auditory nerves inside the cochlea. On the exterior of the head are a microphone, speech processor and transmitter that enable the wearer to adjust the sound for quality and amplification. The semi-implantable hearing aid, however, does amplify sounds, turning mechanical signals into electronic ones and stimulating the internal ear. SOUNDBRIDGE, said Sichel in an interview in his seventh-floor office, increases the volume of sounds in an entirely different way. "I was interested in it for years, and France is the place where it is used the most. I was in touch with the company's branch there, and it sends its experts to train us." Perez noted that while it isn't offered automatically anywhere in the world as part of a basket of health insurance, French hospitals were given permission to implant a limited number per year at no cost to patients. In Israel, the operation is paid for by health funds, but the device itself costs $11.500. The conventional hearing aid, explained Sichel, has a microphone, amplifier and receiver, and sits inside the external ear, thus closing the ear canal to the outer world. But the fact that the parts are close together creates microphone feedback. In addition, cerumen (ear wax) can get impacted in the ear, and there is distortion of higher-decibel sounds. External hearing aids have a wide range of prices from a few thousand shekels up to NIS 18,000 for the smallest and most sophisticated. But some hearing-disabled people can't hear or manage well with them. The Soundbridge has an external portion and an implanted one. The round audio processor on the outside contains the battery, the microphone and Siemens high-quality, fully digital signal processing. The audio processor converts sounds in the environment into electrical signals and transfers them to the implant. The implant unit relays the signal via the conductor link to a tiny "floating mass transducer" attached in a three-hour operation to the incus - one of the three small bones in the middle ear. This amplifies sound and produces excellent sound quality without blocking the ear canal. SICHEL AND PEREZ - who addressed an internal Shaare Zedek medical symposium last month to introduce the device - noted that a hole is not made in the skull to hold the external portion. Instead, a magnet is implanted under the skin on the side/back of the head, and another magnet holds the battery and the rest of the audio processor in place; it can be removed easily when the wearer showers, swims or changes batteries. The exterior part can be covered completely by hair (especially in women, which is an esthetic boon to many. The Soundbridge was "not designed for children," said Perez, but a few have already been implanted in youngsters abroad. It can be implanted in each ear for a full hearing experience, but because of the cost, this is rare. Among the advantages, said Sichel and Perez, is that speech and sounds have a more natural quality. One can even hear high-toned music, they added. The ear canal is open, wearing the exterior part is more comfortable than most conventional hearing aids, and there is no feedback or any embarrassing whistling that can be heard by others. One can understand speech more easily even in noisy surroundings. BUT THERE are limitations, the ear experts noted. "We offer it only to people who don't manage with their hearing aid - and after all, it involves surgery. Theoretically, at least, hearing could be damaged during the implant. There could be electronic or mechanical failure. It isn't good for every type of hearing disability, and won't be of help to those who are completely deaf. If there is no functioning nerve between the internal ear and the brain, it won't help, but if the nerve is only partially damaged, it can." After an Austrian surgeon affiliated to the Med-El company came to Jerusalem six months ago to show them the procedure, Sichel and Perez successfully operated on 62-year-old and 47-year-old women, who are both very pleased with the results. "We are not in a rush to do more. People have high expectations, so we have to choose patients," said Perez. Researchers and otologists are constantly working on new hearing technologies, said Perez. A company named Carina Otologic has developed a fully implantable hearing aid with nothing visible from the outside; the battery inside is charged with electricity via the skull! But there are only about 100 people in the world who have this. It is more expensive than Soundbridge, and there are other potential problems with the Otologic device, they said. "Semi-implantable is the current trend." The 20-bed otology unit, with two full-time doctors and six other part-time physicians, is increasingly busy. "We are developing very fast," said Sichel. "We used to have only 13 inpatient beds. Our clinic visits are also increasing." Neither of them has any explanation for the fact that there seem to be many more cases of bacterial infections of the mastoid bone than they know of in other countries. Maybe it's the weather, they shrugged. Shaare Zedek now performs hearing checks on all 1,000 infants born at the hospital each month (with some help from Hadassah), becoming the third hospital in the country to do so (after Hadassah and Sheba Medical Centers) - even though the cost is not covered by the health services. "We started a year ago with a donation covering the cost," said Sichel. It is unfortunate that screening is not covered by the government or health funds, as the earlier hearing problems are detected, the better they can be treated. "We have found one to three cases of hearing disability or deafness per 1,000 infants," said Perez. The Shaare Zedek doctors urge young people to protect their hearing. The use of MP3 devices or iPods with earpieces and played at high volumes, like attendance at very noisy weddings or musical events, can damage hearing. Babies and young children should be especially protected. Or, as the Big Bad Wolf told Little Red Riding Hood when she asked why "Grandma" had such big ears: "The better to hear you with."