There are two types of structure. The first one is the Surface structure, and the second one is Deep Structure. The surface structure conveys the general meaning of the sentence while the deep structure is a structure in which we identify the sentence's abstract meaning.
“What are you reading?” if we see a simple or surface structure merely asking a question, but in the deep structure, we can extract many meanings from this sentence.
You are What you read. Asking like “What are you reading?” could be meant to ask what the next person is up to. We can judge the personality of a person based on what he or she is reading. Because the things we read decide what our future will be. So asking this simple question could take you a lot more.
To sigh loudly would imply that you are being snotty and you want your way, but it is more personal. You may just be sighing to one specific person instead of trying to draw attention to yourself over a bunch of people, perhaps to gain their attention.
