pipe down

1．call（sailors） away from work with a whistle吹哨唤（水手们）下班

He piped the men down after boat drill．航行实习后他吹口哨解散队员。

2．stop talking；be quiet停止讲话；安静

Do pipe down！I'm trying to work．务请安静下来！我要干活。

The boy kept interrupting the speaker with questions，and every one of us had to pipe him down．那男孩老是发问，打断发言人的话，我们大家只得叫他住口。

pipe up speak up大胆地说

Everyone was afraid to talk to the police，but a small child piped up．大家都怕同警察说话，可是一位小男孩大胆地站出来开了腔。

He piped up near the end of the meeting．会议临近结束时，他起来发了言。