Whats going on with my friend PLZ HELP IM SO CURIOUS?

ok every time were talking were just going on about whatever and in the middle of the conversation i hear a noise coming from him, im not sure what and im like " wait, did you hear that" and hes like " what? i didnt hear anything" so we go on talking again and then i hear it again while were talking and im like " ok seriously wtf is that noise" then it starts to smell and hes like " i dont hear anything lets go somewhere else then" im just wondering like is it a ghost or some or what?