Smart glasses are giving deaf people a head-up-display of live, real-time subtitles, as they chat, right in front of their eyes.

The technology uses off the shelf augmented reality 'AR' glasses that are tethered to a smart phones with an app that turns any speech picked up into text displayed on the inside of the lenses.

"Powerful. It's powerful. I can't under state the power and the importance for people who are hard of hearing all over the world to feel that they don't have to solely rely on lip reading anymore. It's a really big moment," Josh Feldman, a deaf 23-year-old management consultant, said.

The software, called XRAI Glass, was inspired by Dan Scarfe’s observation of his grandfather’s increasing isolation as he lost his hearing.

"There was just a little epiphany moment where I thought, well, hang on a second, he watches TV all the time with subtitles on. Why can't we subtitle the world?," Mr Scarfe said.

The software is still being developed but Mr Scarfe says it can already recognise who is speaking and will soon have the power to translate languages, voice tones, accents and pitch.

"I'm getting a real time stream of subtitled information where ordinarily I might be behind. I might not quite catch everything, but this is giving me a real time narrative which enables me to be informed. It enables me to be involved, enables me to make decisions because I know what is being said," said Steve Crump, founder of DeafKidz International.

XRAI Glass are now recruiting alpha testers who either cannot lip read or struggle to pick up multiple conversations taking place at once, to help perfect the software.