I was reading this article on why women moan during sex. There are so many reasons, and poor fellas, you will never know which one is the real reason. 
- It feels good (yay for him, yay for me)
- I'm trying to keep him on the right track
- The room is too quiet 
- I'm bored
- I'm CUMMING! (YAY!)
- I'm CUMMING! (but its fake)
Why women moan during sex