pin
you can (could} hear a pin drop
意：静极了;静得连针掉在地上都能听见
例，After the curtain came down, it was so quiet that you could hears pin drop.
大幕落下后，静极了，连针掉在地上都能听得见。
PiPe
Pipe down!
用：多用来命令孩子。相当于Shut up! ge quiet!
意：别说了!住嘴!安静些!静一静!
例 .Pipe down, you lot! I'm trying to listen to the news。the radio.
都给我安静些!我要听收音机里的新闻。
Will you pipe down for a moment, Terry? I'm writing a letter.
特里，你安静一会儿，好不好?我在写信呢。
