Researchers are working on lip-reading technology which could be integrated into mobile phones, allowing users to have 'silent conversations'.

The muscles you use when speaking produce tiny electrical signals, even if you don't make an audible sound, which are measured by the technology.

Professor Tanja Shultz of the Karlsruhe Institute of Technology told the BBC: "I was taking the train and the person sitting next to me was constantly chatting and I thought 'I need to change this'.

"We call it silent communication."

The technology uses nine electrodes that are attached to a user's face. These measure the electrical signals, which are then recorded and amplified before being transmitted via Bluetooth to a PC.

Software on the computer decodes the signals into text, which could be 'spoken' using a text-to-voice program. Shultz said it could be integrated into a handset.

Shultz added that while there was currently no mass market appeal, there maybe in the future.

Alternatively, the technology could be used by people who have lost their voice, or as a language translation system.

See also: Boffins create lip-reading computer