SEE, WATCH, HEAR, LISTEN, FEEL, SMELL, NOTICE, OBSERVE + object + bare infinitive

After verbs of perception (see, watch, hear, listen, feel, smell, notice, observe etc.), the infinitive expresses a completed action:

I felt the ground shake once. (I felt it as the ground shook once.)
I saw the burglar climb over the fence and break into the house. (I saw that the burglar climbed over the fence and broke into the house.)
I have never heard them play that song before. (I have never heard that song played by them before.)

In the passive voice, we use a to-infinitive:

The burglar was seen to climb over the fence.

A present participle after these verbs refers to an action continuing over a period of time:

I felt the ground shaking for about half a minute. (I felt that the ground was shaking.)