Same thing happens with me, mainly after 3 or 4 doses. Also guessing by your name I assume you smoke a lot of weed when you come down and I think that has a lot to do with it.
I used to get this quite alot. It's generally from amphetamine type drug (MDMA included) and sleep deprivation mixed with a quiet environment with just a little noise going on (like a fridge humming or slow / distant traffic)..
I wouldn't worry about it.
If the voices start saying things to you.. i'd worry a bit more.. and if the voices start being mean to you.. it's time to stop