So, what would have been a better way to handle the hoard?
I give them some leeway, because it appears the whole sound sensitivity thing in this case is integral to what's happening in the plot, and the writers wanted this to happen. I'm betting on the "W's".
Otherwise, given the constant reminder of how sensitive the walkers are to sound, they should have known the great risk they were taking regarding potentially creating a forest full of walkers. I don't know if we've had any concrete evidence about the scarcity or not of gasoline, diesel, and other flammables, but there was the potential of just lighting a bunch of them on fire if they were bunched up.
Obviously wouldn't get them all, and probably not even a majority, but it could have cut down on the number of mobile walkers they were luring out of the quarry. Also possibly a brick of .22 to put down a bunch of them (they would have had time while they were fortifying for the march and before the semi gave way).