Most men have watched porn. The number might surprise you: up to 98 percent at least once, according to a 2006 Danish study that looked at 18- to 30-year-old men and women. While there's no shame in watching adult entertainment, it's easy to forget that what you're seeing is often staged, scripted and an unrealistic performance of exaggerated pleasure.

So when men who watch porn are having intercourse, that disconnect might make them compare situations and wonder, "Why isn't my girlfriend sounding like they do in the videos?"

I'm sorry to report that, in the real world, many women don't moan during sex. And if they do, it's not the full-throated yowl of uncontrolled rapture you're comparing it to. But this doesn't mean you're doing something wrong.

Here, sex coaches and sex experts explore the reasons your partner is quiet during sex and what you can do to perhaps find a