God yes! Sue is right. I get this too Hopeful and normaly when I'm drifting off to sleep or meditating. I've spoken to loads of others who get the same thing too. So yeh, you're not the only one! :)
Hopeful, Claire Weekes wrote about this. She said that some people hear a noise in their heads like a pistol shot, and that you should be pleased if you hear this because it means your tensed muscles are relaxing. She was speaking of people who were drifting off to sleep, but it makes sense that you'd hear it when you're meditating.
This has happened the last two afternoons when I lay down to meditate and pray. Right when I get very relaxed and I start to drift off to sleep, a PING or POP of sorts goes off in my brain, startling me awake. It's almost like an electrical impluse of some kind. There is no pain or other symptoms that I notice as I'm always laying down and my eyes are closed. This has only happened a few times lately. It lasts just a second and doesn't cause me to panic like other things like that do. I don't know why it doesn't, I can get all worked up when my foot falls asleep! HA! Been on Lexapro for about 5 weeks now and it's been helping alot. Have had no other side effects like this before. Anyone have this?