|MLA Citation:||Bloomfield, Louis A. "Question 979"|
How Everything Works 16 Jul 2018. 16 Jul 2018 <http://howeverythingworks.org/print1.php?QNum=979>.
However, there is one peculiar thing that does happen once a plane has exceeded the speed of sound. You can no longer hear the plane coming because it is outrunning its own sound waves. Instead of having its sound spread out in front of it, the plane has its sound swept back in a cone behind it. The edges of this cone are a shock wave and you experience a sudden pressure rise as this cone passes across you—you hear a sonic boom. A supersonic plane carries this conical shock wave with it at all times and everyone hears a sonic boom as this shock wave sweeps across them. What you should remember is that the sonic boom doesn't occur when the plane "breaks the sound barrier"; the sonic boom is a continuous feature of a supersonic plane that you hear as its shockwave passes you by.