Intervene has a positive connotation (隐喻). When someone intervenes something, he/she generally comes in between two parties who are in conflict(冲突) in some manner(方式). By intervening, they attempt to resolve the conflict between the two parties.
Intervene是调停他人矛盾的意思。这个单词是褒义词。
For example, two people are arguing, and someone else intervenes to try to stop the argument. Good behavior, and it has a positive connotation.
UN successfully intervened those two countries stopping fire on the border.
联合国成功地调停了那两个国家在边境线上的武装冲突。
Interfere has a negative(负面) connotation. It doesn't necessarily have anything to do with two parties in conflict or even more than one party at all. It implies someone disrupts(干扰) or disturb(烦扰) someone or something.
Interferes is to get in the way of someone else doing something. So, if I'm trying to get my work done, and you interfere me, you're stopping me (or at least disturb me) from getting my work done. There's nothing positive about it. It's entirely negative.
Interfere是干涉、干扰他人的意思。也就是说他人的工作或生活很正常，但被不期望的人或事干涉打扰了，导致原来的节奏被打破。因此这个单词是贬义词
Examples:
The voice will be interfered if you put two speakers in the same place.
如果你把两个喇叭放一块就会出现声音的相互干涉。
The weather interfered the results of the experiment.
天气条件干扰了试验的正常进行。
My brother intervened in my studying to improve my scores obviously.
在我哥哥的积极干预下，我的学习成绩进步很明显。
