A Purdue University researcher's innovation may make it possible for people with severe hearing loss to hear high-frequency sounds.

Joshua Alexander, an assistant professor in Purdue's Department of Speech, Language, and hearing Sciences, says conventional hearing aids do not help listeners with severe hearing loss because their pitch range is limited. This means “everything is placed into a very narrow area which makes different speech sounds too similar to one another,” says Alexander. "Current hearing aid technology works best for people with some residual ability to hear these pitches, but there are too many challenges for it to help listeners with a very restricted pitch range."

Alexander tested variants of existing hearing aid technology, which use algorithms to move information from higher pitches to lower. He discovered what listeners needed to enhance perception in the new pitch range; and then he designed an algorithm to accommodate these needs.

"Unlike other algorithms that simply shift high-frequency sounds to a lower pitch range, this algorithm mirrors and flips them. By moving the highest pitched speech sounds, like "s," to the lowest pitches, the listener can more easily relearn them.”

The algorithm takes advantage of other differences between speech sounds to enhance perception, and multiple features can be customized. It is meant to complement existing hearing aid technology, and may be used in conjunction with cochlear implants, which are surgically implanted electronic devices.

"A new protocol is to give the person with a cochlear implant a hearing aid, too. Implants give the high pitches that a listener is missing, but not the low," he said. "The algorithm could provide redundancy as the listener hears high pitches from both the implant and the hearing aid."