Researchers are developing an electric retainer that could allow the hearing-impaired to ‘listen’ through their tongues.

The retainer will eliminate the need for expensive cochlear implants for those with hearing loss, researchers said.

The technology relies on a Bluetooth-enabled earpiece to detect sound and send electrical impulses to the electrode-packed retainer that wearers press their tongue against to ‘hear’.

"It’s much simpler than undergoing surgery and we think it will be a lot less expensive than cochlear implants," said John Williams, associate professor in the Department of Mechanical Engineering at Colorado State University and the project lead.

Williams was interested in neuroscience and sensory substitution – training the brain to receive information from another source.

The tongue contains thousands of nerves and the region of the brain that interprets touch sensations from the tongue is capable of decoding complicated information.

"What we are trying to do is another form of sensory substitution," Williams said.

Unlike hearing aids, which amplify sound, cochlear implants circumvent damaged areas of the ear and stimulate the auditory nerve directly.

Microphones outside the ear detect sounds and send them to a speech processor, which analyses the information and transmits it to a receiver where it is converted into electric impulses.

The implant sends those impulses directly to the auditory nerve. With training, the brain learns to recognise these impulses as useful sound information.

The CSU device operates very similarly except electric impulses are sent via Bluetooth to a retainer-like mouthpiece packed with electrodes.

When users press their tongue against the device, they feel a distinct pattern of electric impulses as a tingling or vibrating sensation.

The idea is that, with training, the brain will learn to interpret specific patterns as words, thus allowing someone to ‘hear’ with their tongue.

Williams and colleagues have spent the past year building and testing prototypes of the technology.

Their initial results are promising and they have filed a provisional patent for the technology and launched Sapien LLC, a start-up company, to help advance the technology.

Williams is also working with Leslie Stone-Roy, assistant professor in the College of Veterinary Medicine and Biomedical Sciences, to determine which parts of the tongue detect electrical impulses and if those areas are consistent from person to person.

"Basically, we are mapping the nerves on the tongue.

There isn’t a lot of information out there about the nerves on the tongue and their ability to sense electrical impulses," Stone-Roy said.