Gotta love that "Starship breaks the sound barrier during launch" image with the shockwaves visible. NO that is not what happens because the sound barrier was broken, the rocket was already going trans- or supersonic and the resultant shockwaves became visible briefly due to atmospheric conditions. Shockwaves do not spontaneously become visible at the point of transition.

Nonetheless we're going to see that image pasted over and over on social media stating that it's the transitional indication of breaking the sound barrier.