What is the simplest way to explain a sonic boom that is still technically correct?
I will try to explain the principle, briefly and practically as you requested.

Imagine that we have an airplane flying in position 1. It is flying at supersonic speed.



Good, now this airplane moves forward. But it is not the only one moving forward, the perturbation that the airplane produces over the air moves as well, but at a different speed, the speed of sound. In the next figure you will see that the perturbation (or pressure wave) moves less distance than the airplane, which moves from 1 to 2.



The airplane keeps moving to position 3, and at position 2 there are some perturbations (pressure waves) that are also generated and also move as speed of sound. However, I have smartly selected a perturbation that reaches exactly the same point in space that the perturbation (pressure wave) that I selected is reaching as well. So both perturbations meet at the same point.



As you imagine these two are not the only perturbations (pressure waves) that are meeting at this point, there are several points between 1 and 3 that also generate perturbations that join. Actually, this is also not the only point in space where perturbations (pressure waves) join together: there is a line that envelopes the points where the pressure waves meet at each instant. Well, actually a surface in 3D.



OK, if you do the same with a better painting tool than me&hellip; you draw the same but also evolving with time like this:


Which is the image in Wikipedia. What is the effect that you experience?



So the orange observer that is located in advance/before the blue lines does not feel any perturbation due to the airplane, nor hear it, as the pressure wave have not reach him yet.

However, the green observer has already felt the airplane passing by and sees how the air is altered by the airplane (imagine that you are close enough).

Finally the brown observer is just in the middle, coming from a region which has not yet experienced the perturbations made by the airplane and finds suddenly a concentration of perturbations (pressure waves) as described above. That is a sudden change in air flow properties and is experienced as a sonic boom.

To give a real end to this, notice that the further you are from the airplane the less strength the pressure waves have when they arrive at the blue line, making the sonic boom less and less intense.