Tiny device that heralds the end of unsightly hearing aids

The Lyric is programmed for the specific hearing needs of each wearer but its settings and volume can be adjusted or turned off altogether

A new kind of hearing aid that can be worn 24 hours a day for up to four months at a time has been hailed as the answer to the problem of unsightly devices that overamplify noise and squeal with feedback. The invention, which fits inside the outer ear canal just a few millimetres from the eardrum, is said to be the only hearing aid that is completely invisible when worn; users can keep it in when they shower or sleep.

The proximity of the amplifier to the eardrum improves performance and allows people to distinguish individual sounds in a background of noises – the so-called "cocktail party effect" – when it is difficult to hear one voice in a group of people. The Lyric hearing aid, designed by a retired professor at the University of California at San Francisco, is currently sold only in about a dozen clinics in California, Florida and New Jersey but it has proved an instant success with Americans desperate for an alternative to the traditional model.

The inventor, Professor Robert Schindler, who markets the device through his company InSound, said he had suffered hearing loss for most of his life but, since using the Lyric, he was able to hear certain sounds for the first time – such as the "ping" of a triangle in an orchestra. "I realised I had not heard it before. That was a very exciting moment for me," he told The New York Times.

A spongy material with anti-bacterial properties surrounds the Lyric to stop it rubbing against the skin. The material is also water permeable and allows moisture to escape from the ear canal, which could otherwise lead to an infection. Patients must be fitted with the aid by a specialist and continue to wear it until the battery wears out, at which point it is replaced with a completely new device. In emergencies, users can remove the device themselves with a little magnetic instrument.

The Lyric is programmed for the specific hearing needs of each wearer but its settings and volume can be adjusted or turned off altogether. The company says its current model is suitable for about half of all people with hearing loss because of the individual differences in ear canal width but the device is being redesigned to fit about 85 per cent of hearing aid users. It is aimed at people with mild to moderate impairment who prefer an unobtrusive aid that is worn much like a set of disposable contact lenses.

Mike Waufle, a baseball coach whose hearing was damaged by gunfire during his army service, told The New York Times that his life had been changed by Professor Schindler's device. "I teach a lot in a classroom as a coach but, when I would wear a hearing aid, my voice pattern wasn't very good. – it was all over the place. I just took it out most of the time. I missed an awful lot," said the 53-year-old. "Now my voice pattern is so natural and I can hear so much better."

Angela King, of the Royal National Institute for the Deaf, said: "Companies have been exploiting the exciting sound-processing potential of digital technology to produce 'intelligent' aids that are increasingly responsive to the sound environment. Now we are also seeing designs that look better, are more comfortable to wear and give a more natural sound quality.

"People were often put off getting hearing aids because they thought they would look horrible or would not help much – but that is no longer true. Digital hearing aids are available free on the NHS and we are campaigning to reduce the unnecessary long waits for equipment that can transform people's lives and reconnect them to friends and family."