Yesterday my boyfriend and i laid down for a nap. When in half sleep I heard 3 knocks, 3 times on a hollow wooden door. Our house contains no door that would make the sound i heard. When asked, later that night, my boyfriend said that he heard it too. Previous people (only males) who have been friends with me will often hear 3 taps 3 times from outside their windows. Like each individual window and door.
Anybody know what that is?