The 38th Company often found itself working against the Emperor's Children at every opportunity, and as a result found itself with a wealth of stolen noise blasters. These weapons were effectively useless in the hands of ordinary soldiers and Astartes, who couldn't perceive or manage the precise pitch cascade necessary to aim the weapon properly. By sheer coincidence, bat ponies' echolocation allows them to properly perceive the clashing sound waves and aim them for optimum effect. The weapons did need to be downsized for the smaller creatures to handle and to prevent lethal sonic feedback that their weaker constitutions couldn't bear, and thus the echo cannon was born.
for Age of Iron