This can happen in air as an airplane travels faster than sound.
Then this shock wave follows along behind the airplane and eventually
touches the ground as shown in Figure 12.21. As this shock wave-this
wave front of increased pressure-goes along the ground, it will
be heard as a loud noise or felt as a burst of increased pressure.
We call this a "sonic boom" and it may rattle or even
break windows of buildings as it passes by. That is why supersonic
flights are kept away from inhabited areas.
This shock wave of wave fronts piling up on one another also occurs
when a boat travels through water faster than the speed of the
waves across the surface of the water. Then a distinctive "bow
wave" is produces as shown in Figure 12.22.