Hahaha, I'm told I'm the same way. I can have a great convo with the MPA as we start into the session but when the stuff goes down I tend to quiet down. That goes for SPs and civvies too, during the deed. I have to work on that, because as sweetbabyjamie said, it's hard for your partner to get a reference point if you're not giving them anything to work with. It just feels unnatural for me moan, groan or grunt during sex, no matter how good it is.