A: Don't make a noise here.
B: What's wrong?
A: Your brother is down in the dumps.
A:He got a low mark this time.
be down in the dumps：忧郁，闷闷不乐
e.g.Molly's been moping around all week and I have no idea why she's so down in the dumps.
e.g.Rob has been down in the dumps ever since Gloria broke up with him.
e.g. He was down in the dumps after losing his job.
e.g. He's one of those people who can't stand his own company.As soon as he finds himself alone he gets down in the dumps.
1. make a noise：吵闹，喧哗，成为众人谈论或注意的对象
e.g. Don't make a noise in the library.
e.g. He was eager to make a noise in the world.
e.g. We were very careful not to make a noise.
2.get a low mark：考试没有考好，得到低分
e.g. You get a low mark,for one thing,because you did not do your homework.
e.g. I'm sure I've got a low mark.