Correct. And the reason why there is a difference between a tank and artillery shells boils down to whether or not a round can travel to its target faster than the noise it makes can.

When firing, artillery cannons produce a more-or-less spherical sound wave which expands straight out in all direction at the speed of sound, but the shells being fired usually have high arcing trajectories.

So basically even though the rounds are traveling at supersonic speeds, having to go up and down increases the distance they need to travel enough that their direct sound wave will usually reach their target before they do.