I'm pretty well up on mid-18th c. military history, but I confess I haven't made a systematic study of this issue, and a brief survey of major battles hasn't turned up any examples. So I'll ask - are there examples of 18th c. corps/wings/columns/whatever marching into battle on the scale and time-frame represented by this rule?
As a design concept, "sound of guns" looks to me like a hold-over from NCP/AACW and I'm not sure it belongs in ROP. Retaining corps (or "columns") gave me some concern for how successfully an engine originally created to simulate early- and mid-19th c. warfare could be adapted for mid-18th c. conditions. The operational flexibility represented by the "sound of guns" rule seems to me the prime example of this problem. To me, it seems anachronistic - I'd be happy to be proven wrong.
