Imagine chatting with your mates on your mobile without making a sound... It might sound impossible, but a new invention could let you do just that.
Researchers have created technology for a lip reading phone that they say would let people have silent conversations.
It works by measuring tiny electrical signals that are produced by the muscles you use when you speak.
The would would record the signals and use them to generate a computerised voice in another handset.
Professor Tanja Shultz, from the Karlsruhe Institute of Technology, said she came up with the idea on a noisy train.
The kit for the lip reading phone is still in its early stages
"I was taking the train and the person sitting next to me was constantly chatting and I thought 'I need to change this'," she said.
"We call it silent communication."
But don't expect to see the phone in shops any time soon as it's still in its early stages of development.
An early model of how the technology works has been on display at an electronics fair in Germany, using nine electrodes stuck to a user's face to register their facial movements.