New voice
Beatle George Harrison and actor Michael Douglas are among a number of celebrities who have developed throat cancer. Removing the larynyx, voice box, is the more usual treatment for large tumours and a small valve inserted into the windpipe is the most common way to restore speech after a laryngectomy. A local throat surgeon looking for a more user-friendly solution inspired the team from the University of Hull and the University of Sheffield to come up with a device that can interpret facial movements as the wearer mouths a word and reconstruct the intended speech.

Voice recognition training
‘What we quite simply do’ says Dr Jim Gilbert the project’s leader, ‘is put small magnets on the tip of the tongue and on the lips. At the moment we are just Superglueing those on, but eventually they would be injected or embedded. We have some magnetic sensors that sit around the front of the face, monitoring the magnetic field as the mouth moves and recognising from those movements what type of speech the person is trying to produce.’

The movements of the magnetic field are individual but consistent for each individual’s speech. Gilbert points out the need to train the system before the person has the laryngectomy, ‘you record the movements of the magnets and add the speech that movement produces. After the laryngectomy you can use the magnetic signals to say that looks like this word.’

Tip of your tongue
Getting experimental data is a major challenge at the moment, so Gilbert and his team are Superglueing the magnets to their own tongues. The next big step is to turn their lab kit into a smaller and more attractive microphone or Bluetooth earpiece. So they are working on a consultation process with potential users. The quality of the speech depends on how many sensors and magnets are present. The best signals are obtained from a magnet on the tip of the tongue.

Using magnetic fields rather than acoustic signals is an exciting departure for the team. ‘There’s a lot of interest in what’s called silent speech, the idea is that you can be on the phone and have a conversation without actually speaking,’ Gilbert explains. ‘Obviously someone isn’t going to inject magnets into their tongue in order to do that. A temporary device could allow covert work or communication in a very noisy environment where the acoustic signal gets buried in the background noise.’