I've heard those external voices too, the ones that are brief, except I hear them a lot. I hear what sounds like chatter, it's usually muffled, and I think someone is in the building (usually at work) and I check and I'm the only one in here. I've heard laughing as well, and I've heard the whole "HEY!" thing too, and I've even heard my name called. It happens a lot to me when I'm in that zone between waking and sleep. Sometimes it sounds like a party is going on. I can hear singing too. I've wondered sometimes if they're spirits trying to contact me. I try to talk to them but if they do respond, I can't usually understand what they're saying. I have a voice in my head too that I talk to. I rely on her for advice, like gut instinct type stuff. She's like another me. Sometimes I worry that people can read my thoughts, like the government, and they'll come to get me, so I try to think positive thoughts, but sometimes those really negative ones get in there. I also worry that the government is watching me through my TV and my computer. I used to drape towels over my windows at home because I was afraid the neighbors were spying on me for the government.