The only sound I made after that was a weak tinkling of bells. (1.81)
Susie's jingly cap is a homemade symbol of her mother's love and care. Harvey perverts it, using it to gag Susie while he rapes her. It becomes a symbol of her loss of breath and voice. When Len Fenerman recovers her hat and shows it to Abigail and Jack, it becomes a symbol that great harm has come to Susie. The hat though, also leads us back to the roots of the American horror story – yes, back to Edgar Allan Poe.
In Poe's "The Cask of Amontillado," a tale of revenge and murder, the narrator murders Fortunato (dressed like a jester, complete with jingly cap) by walling him up in a tiny underground space. Before the narrator puts in the last brick of the wall he's enclosing Fortunato in, he makes sure that Fortunato, like Susie, no longer has voice to protest. He says that, at the end, "There came forth in return only a jingling of the bells." We also think of bells as tolling for the dead. In the case of both Susie and the ironically named Fortunato, the jingling of bells are one of the last sounds they hear.