Pretty Much Dead Already - S2-E7
Continuity mistake: Deleted footage/special release only: Carol confronts Daryl about the boy being held hostage inside the barn (following Sophia's death), reasoning with him about pretending not to care when he truly does. At one point he moves to her, almost in her face. However, the following shot shows only a close up of Carol, implying they are standing feet apart, which is not the case. (00:24:10)
Answer: Walkers are attracted to noise, they can tell who's dead and who isn't dead, in S1 when Rick and Glenn cover themselves in walkers' guts they're able to get far by walking through the herd of walkers because they smell like they're dead, but as soon as the guts get washed off by the rain the walkers immediately attack them, if you draw attention to yourself they will attack you which we've seen that many times throughout the series that it's not always successful. Whether you're covered in guts hiding under dead corpses or under a car.