Astronauts in space spooked by mysterious knocking sound that no one can explain

Astronauts in space spooked by mysterious knocking sound that no one can explain :

China’s first astronaut says he heard mysterious knocks during his first flight in space – but no one has been able to explain the cause of them.

Astronaut Yang Liwei said the strange noises left him feeling very nervous and he looked out into the vast emptiness of space but couldn’t see anything out of the ordinary.