The ringing bells on Fortunato’s cap naturally attract attention. This makes it that much more of a problem for Montresor, who wants to get Fortunato down off the crowded streets into his catacombs. Fortunato is wearing the most conspicuous kind of a costume. Poe could have given him any kind of costume but he deliberately made it not only gaudy but noisy. The biggest conflict in the story is Montresor’s problem in getting Fortunato down below without being recognized himself. He didn’t want anybody to remember seeing him with Fortunato on the night Fortunato disappeared. By making Fortunato so conspicuous, Poe makes Montresor all the more inconspicuous in his black cloak and black mask. He is almost like a shadow. Inquiries will be made. Many people will remember seeing Fortunato, and a few will remember that he was with someone---but no one will be able to tell who he was with. Montresor has plenty of foresight. He knows that Fortunato’s disappearance will be talked about for years. He himself will have to keep asking if there is any news about his “good friend” until the authorities give up their investigations and the matter is finally forgotten.
I would agree with the symbolism of the bells in general, but there is also a more specific meaning that applies here. Fortunato is wearing a costume for carnival, and the hat has bells on it. The ringing bells indicate his nervous motion, that he is upset, that he has moved physically, and, throughout, that this is Carnival, the time when the world is turned upside down. This makes the entire story deeply ironic, for the narrator is essentially walling a clown into the brick work, and the bells remind us of this.
Throughout Poe's "The Cask of Amontillado," bells and the ringing of bells signify death. In this tale, the "jingling" of bells occurs numerous times.
Historically, the ringing of bells told all hearers of a death. The quote from poet John Donne should have been "ringing" in the protagonist's ears: "Ask not for whom the bell tolls, it tolls for thee."