有be heard doing 的用法.请看例句：
1.I often hear him sing in the morning.(改为被动语态）(我经常听到他早晨唱歌,hear sb.do sth.）
He is ofen heard to sing in the morning.
2.I heard him singing just now.(改为被动语态）("刚才我听到他正在唱歌”hear sb.doing sth.）
He was heard singing just now.
我是复制别人的.