The contract includes the design, fabrication, and testing of an aircraft that can break the sound barrier with a sound that's just about as loud as a car door closing. (newscientist.com)
During a 4 minute 20 second free fall, he became the first person to break the sound barrier without a plane. (discovermagazine.com)
So if it continues the way it's going, we may break that ceiling, like breaking the sound barrier. (discovermagazine.com)