[quote=Leidenschaft]
The Imperial Legions owe a lot of the way they work with the Roman Legions, I'm assuming Post-Marian Legions to be exact. Legions in battle formations were often packed nice and close to make full use of shield-walls, so they would definitely be hearing it, and if they couldn't, the order would be carried along on the line of commanders assigned to each cohort and contubernium.
[/quote]

Wont matter much how close, unless no one is wearing a helmet, no one on the entire battlefield is shouting, no horses hooves making a sound on hard earth, and the married of other noises plaguing a battlefield. There is a reason even the roman legion used trumpets and banners.