In Dev 1.71.141457:
When you are going supersonic in a jet, you can hear your own sonic boom, when goining into the targeting camera.
Worked for me almost every time i went into the camera, with both Black Wasp and Shikra, although the delay until you could hear the boom was changing.
i haven't been able to figure out a pattern how it changes, but durations were between 1 and like 15 sec.