The sound barrier is the point at which an object moves from transonic to supersonic speed. You might hear a "boom" sound.
The question was whether a person could break the sound barrier outside of an airplane. Felix Baumgartner wanted to travel into space to answer this question. On October 14, 2012, he celebrated the 65th anniversary of Yeager's feat by trying to break the sound barrier himself. Baumgartner broke the sound barrier and set a world record by jumping 24.26 miles at speeds up to 833.9 miles per hour. He successfully landed in New Mexico.