A sonic boom occurs when an aircraft exceeds the speed of sound. Normally, whenever any aircraft travels, it creates pressure waves in the air in front of and behind it — similar to how a boat produces waves in the water.
Those pressure waves travel at the speed of sound. So when an aircraft surpasses that speed, it compresses the pressure waves in front of it to the point they produce a shock wave.
That shock wave is what you hear as a sonic boom.
A sonic boom can generate sounds of up to 110 decibels, similar to a thunderclap or explosion strong enough to shatter windows and cause tremors. Trained fighter pilots become acclimated to traveling at Mach speeds, but not so much the average commercial airline passenger.
There are no commercial supersonic planes currently in operation since the permanent retirement of the Concorde. Developed in the 1960s, the Concorde was the first supersonic passenger-carrying commercial airplane built by the UK and France. Traveling at speeds up to Mach 2, the aircraft reduced travel between New York and London to only three hours.
Only 14 Concordes went into service before it was retired in 2003 due to its costly operation, risks, and noise.
The X-59 aims to change that.
The Quesst mission seeks to reduce "the loudness of a sonic boom reaching the ground to that of a gentle thump, if it is heard at all," the agency said.