hear表示“听说”时后面常接that从句。例如：

I heard that he was ill. 我听说他病了。

hear of和hear about“听说”常可互换使用，其后接人或事。例如：

I have never heard about him. 我从未听说过他。

I have never heard of such a thing. 我从未听过这样的事。

I've never heard of anyone doing that. 我从未听说有人做那种事。

Have you heard about Julia coming to Geneva? 你有没有听说朱丽娅到日内瓦来了?

hear, hear about, hear of 都可以表示“听说”，怎么区别它们呢？

     【答】现在时形式的  I hear (that), I see (that) 和 I understand (that)  常用来引出听到或看到的各种消息，通常译为“听说”，that 引导一个宾语从句，that  可以省略。如：

      I hear (that) Alice is expecting a baby. 听说艾丽斯快要生孩子了。

      I see (that) the firemen are going on strike. 听说消防员罢工了。

      "I understand you're moving to a new job.""Yes, that's right."

      “听说你要换新工作了。”“是的，没错。”

       （以上例句摘自《牛津英语用法指南》第四版482节）