Yes/No Question Intonation and Pitch
"Yes/No Rising Pitch" in Unmarked Questions
Yes/no questions--those are the ones whose answers can be a "yes" or a "no"-- tend to end in a rising pitch pattern. This is opposite of the pattern for wh- questions, whose pitch boundaries normally fall.
The change in pitch usually begins on the pitch word of the question, then continues through the end of the sentence. (Pitch words are also often the final content word and the word of the sentence that receives the most emphasis.)
The following sentences are unmarked, meaning their intonation is being used in the most neutral manner. No additional nuance or emotion is added to the sentence.
"Yes/No Falling Pitch" and its Purposes
Using a falling pitch in a yes/no question can show that the person asking the question already knows the answer. Why would a person ask a question if the answer is already known? Maybe the asker wants confirmation, or is using the question itself as a reminder. It's also possible that the question is alluding to a wh-question.
For instance, asking, "Do you have Dave's phone number?" with a falling pitch could show that the asker knows the responder has the phone number and is actually asking to be given the number. As with much of English, there are multiple ways to communicate the same information.
"Yes/No Emphatic Falling Pitch" and its Purposes
Giving extra emphasis to a pitch word in a yes/no question, and following it with a more dramatic fall is the most marked form of the question. The "Yes/No Emphatic Fall" can show anger, annoyance, or impatience.
Asking the question, "Do you have John's phone number?" in an emphatic fall could signal that the asker has asked this question multiple times before is is getting impatient waiting for an answer.
Asking "Did you understand that?" in an emphatic fall could sound condescending or snobby to a listener. Use the Yes/No Emphatic Fall intonation pattern with care.