主動語態(tài)中,hear只能接不帶to的不定式或動名詞作賓語,即：hear sb do ；hear sb doing
在被動語態(tài)中,要將不定式前加上to,即：be heard to do；be heard doing

你所提是在被動語態(tài)中,所以be heard to doing不存在.
be heard to do被聽說將去做某
be heard to be doing 　是to do 的進行時：被聽說正在做某事
be heard doing被聽說（近期）一直在做某事

另,不定式一般時、進行時和完成時的區(qū)別
He is believed to come.(=It is believed that he will come.) 要來,還沒來
He is believed to be coming.(=It is believed that he is coming.)正在來路上
He is believed to have come.(= It is believed that he has come.) 已經(jīng)來了