(1)hear +宾语，是主语直接亲身听到/听见

She heard no further sounds  

她再没有听到别的声音了。

You can hear commentary on the match in about half an hour's time. 

大约半小时后就能听到这场比赛的解说了

The trumpet can be heard all over their house. 

喇叭声整栋房子都能听见。

(2)hear of +宾语，是主句间接（从某人/某个地方/某本书/杂志）听说/了解到宾语的情况

Many people haven't heard of reflexology.  

很多人没听说过反射学。

My mother heard of this school through Leslie. 

我母亲是从莱斯利那里知道这所学校的。

I heard of the decline of the Roman Empire, chivalry, Christianity, and kings.

以上属于第2种用法“通过某种渠道/途径间接听到/了解到的罗马帝国的衰落”