Reports from Iuka show that Grant and Ord *could* hear the sounds of sporadic fighting, which is exactly what was going on in Rosecrans' front. I think the problem was that Rosecrans, who knew the country, described the area south of Iuka as open and perfect for a pitched fight. Instead, Rosecrans ended up in broken fighting over difficult terrain all day ... cannons deployed in the small open spaces would be charged from cover by the enemy and taken, then retaken, then taken, then retaken again. As such, Ord and Grant didn't hear the expected continuous roll of artillery that would indicate a pitched fight ... instead, they heard scattered volleys, and occasional firing of artillery.

I don't buy the assertion that residents in Vicksburg could hear the fighting and Johnston at Calhoun Station could not ... in fact, the actual Champion Hill hillside would reflect sound directly *towards* Calhoun Station, not away from it ... at least from the Jackson Road side of the battlefield.