Did you hear that?

When I was 15 and my sister was 10, we shared a room at my old duplex, the duplex was old military housing, and there are several times we experienced paranormal things while living there, dark shadows here and there, a glass being moved when my dad left and came back shortly with no one in the house, and voices, there were two incidents of that, one was the summer after we moved in and my sister, and my cousin and I were sleeping in the bedroom and we're all almost asleep and we all heard a man's voice say "What?" and we all woke up and said "What?" to each other, we were pretty spooked, the second incident happened when I was 17 and my sister was 13, we were both sleeping and we heard really loud "Hi dad!" and it was so weird, because when I heard it, it sounded muffled and strained but my sister said she heard it very clearly, to this day we talk about it every now and then, and it still creeps us out.