Researchers have placed electrical rods on the brains of participants and worked with them while the participants were in conversation. They found that brain processes the information in the speed between one to 8000 hertz.
One of the words reproduced by scientists was "Structure".
Prof Robert Knight, one of the researchers from the University of California at Berkeley, said: "This is huge for patients who have damage to their speech mechanisms because of a stroke or Lou Gehrig's disease and can't speak.
"If you could eventually reconstruct imagined conversations from brain activity, thousands of people could benefit."