The room doesn´t need to be ´´quiet´´ per say. Just covering them should suffice... unless you are planning on a rave or house party.
One of my birds doesn´t get covered at all. My Sydney lives alone and has a nest box, so if he wants darkness he goes in there. in the summer I cover him sometimes. But he is a strangely quiet lovebird.
I cover my other birds at about 9 or 10pm and uncover them at 8am.
Plus your question is ¨How much time do lovies need to spend asleep in a normal day?¨- All my lovebirds have a good snooze in the afternoon too (uncovered). So if you mean in total, you will have to count that on too.
I´m sure many lovebird owners have different schedules