What you describe reminds me of experiences I have had while astral phasing. In what Robert Monroe refers to as Focus 12, for example, one begins to see swirling colors, patterns and shapes. Also, there are sounds that occur such as pops, bangs, other loud noises, and even music.
One time I was phasing I heard a really loud sound. It brought me right back to C-1 (physical). I looked around and saw my wife asleep, and the cats hadn't moved. That is when I knew it was a non-physical sound (otherwise at least the cats would have run for cover) [:)].
So it sounds as though you had a similar experience by way of astral projection.
Very best,
last night i AP'd and when i did i found myself in my room with differatn changes which is well common ut the thing that scared me was a very loud BOOMING going on, it felt as if there was an explosion in the house,or an earthquake was taking place but i have no idea what it was. can anyone explain this strange noise? has anyonelse heard it?