Birdsong, for example, is a sound which most people find reassuring.  There is a reason for that. Over hundreds of thousands of years we've learned that when the birds are singing, things are safe.
比如鸟鸣，这种声音对于大多数人而言 都是一种安慰。 这正是在经历了成百上千年 我们认识到鸟的歌声是安全的表现的原因。