Sonic boom

A sonic boom was a burst of sonic disruption that usually occured when something large broke the sound barrier.

This was the case when the Sycorax ship entered earth's atmosphere. The wave stretched on for miles with London as the epicentre. Glass windows all over the surrounding area were blown apart by the force of the blast.

The same thing did not happen when the spaceship left the atmosphere, possibly because it was destroyed moments after. (DW: The Christmas Invasion)