1.To some extent, facebook helps air out dirty laundry.
在某种程度上，脸书能帮助人把自己不光彩的秘密说出去。
dirty laundry:
(idiomatic) Unflattering facts or questionable activities that one wants to remain secret, but which some other may use to blackmail with.
If you don't tell me why you did it, I'll air all your dirty laundry to your boss.
2.I was trying to keep the party a secret, but Mel went and let the cat out of the bag.
我尽力守住要举办聚会这个秘密，可是梅尔一去就说漏了嘴。
let the cat out of the bag:
(idiomatic) To disclose a secret; to let a secret be known, often inadvertently.
Synonyms:
(to let a secret be known): spill the beans, talk, tattle, blab, peach (obsolete), babble, sing
3.Lower your voice because walls have ears.
小点声，隔墙有耳。
walls have ears:
There is a risk of being overheard, so be careful what you say.
