re: Weird sleep experience last night

There have been a couple of times where I have been on the very edge of sleep and dreaming just before you really fall sleep for bed. The other night I was half way in and out of consciousness and heard this knocking noise on wood. In the middle of the night in all dark, it isn't a sound one wants to be hearing. I laid there and listened but never heard it again. I think it was in my dream state I heard this noise. I've had this happen kinda recently before but this time was very clear and really had me questioning if it were in real life or not.