I practice Qi Gong which is a form of meditation originating from China.
During meditation practice, I would routinely hear odd noises coming from my television. Almost like someone was flicking the plastic portion of the back of my TV with their finger. I meditate with my eyes closed and every time I would hear one of these noises it would cause a "jolt" and I would see a flash of odd discordant colors on the inside of my eyelids.
At first I didn't think anything of it, I have a large plasma screen television, and maybe that's just the noise it makes while cooling down. Also, during meditation, you in theory, create an electromagnetic field. I thought perhaps this somehow was interfering with the T.V. itself, and I would usually meditate after watching T.V.
One night I decided to keep my T.V. off for an entire day, then meditate. The same exact noises started coming from my computer monitor on the other side of the room. I unplugged both monitor and television, and the "tapping" noises started coming from both television and monitor intermittently. This makes no logical sense, if there is no current running through the television, it shouldn't be making any noise. This noise only occurred while meditating, and only at night.
At this point I'm beginning to doubt my sanity for a bit, so the next time I meditate, I turn on the voice recorder on my phone, and place it directly in front of my television. I meditate for around 20 minutes, then check the recording. You can clearly hear the sound of tapping on glass(the screen is glass). I play this for my GF to make sure I am not insane, she hears it too.
So I start researching this and according to Qigong books, performing QiGong can actually attract malevolent entities (demons) due to (Long story, it just does).
Since both my television and my computer monitor are in the basement, I decide to start meditating in my living room. My living room has a couch located directly in front of a bay window, which is where I choose to sit and meditate.
Everything was fine for about 5 minutes, and I think I am in the clear when all of a sudden I hear the same freaking "tap tap tap" LOUDLY on the glass window located directly behind my head. I freak right the F**k out and turn around, turn on the outside lights, there is nothing there. Nothing at all. At this point I "know" there is something living in my house.
So for the following weeks, I tried my best to just ignore the noises and sounds. Somehow, knowing there's something there somehow made it worse. While meditating I sometimes could feel some awful presence directly in front of my face. I would open my eyes and would see nothing. It is incredibly alarming I would hear weird noises coming from the laundry room connected to my basement. I would hear someone using the bathroom, and the toilet flushing when there is no one left in the house.
This has persisted for over 3 months now. I still don't know how to get rid of it.