A device usually used to enable deaf people to hear could help millions who are hard of hearing but not helped by conventional hearing aids, a new study finds.

About 26 million American adults suffer from loss of high-frequency hearing, which makes speech recognition difficult. For some, hearing aids don't help.

Cochlear implants have been used for adults and children who are deaf or profoundly hard of hearing, but they have not been considered suitable for people who have lost high-frequency hearing but still can hear low-frequency sounds.

Researchers at 10 medical centers and private clinics in the U.S. implanted hybrid cochlear implants into one ear of 50 men and women. All still had sufficient low-frequency hearing, which forestalled use of a regular cochlear implant.

The hybrid implant differs from the traditional device in that it has a shorter electrode, which does not have to be inserted as deeply into the inner ear. When placed correctly, the technique preserves more residual, natural, low-frequency hearing and augments high-frequency hearing with electrical stimulation, the researchers said.

A year after receiving the device, 45 study participants showed overall improvement in their hearing and speech recognition. None of the subjects' hearing and speech recognition got worse.

The device costs $30,000 and involves an operation that typically takes less than an hour to install.