As noisy as he wants to be. I like to know that what I am doing is having the desired effect!
What ever amount of noise he/she needs to express the feeling that is running through their body.
Why would you care unless there is a privacy issue.
It doesn't really matter how much noise he makes, as long as it doesn't sound like the barking of a dog or the screaming of a pig. In that case I would just start laughing. Ofcourse, an appreciative moan is nice to hear, but so is the quickening pace of his breath, or the way his muscles flex and clench. To me the body language is way more important than sound, even though sound is very welcome.
The louder and more sensual the better, love a woman who expresses herself in the bed, or the forest, or where ever she may be at that moment in time.
It's a time and place thing - at home I'd want enough to let me know that he's enjoying it without keeping the neighbourhood awake. For a quick handjob during 'night-time' on a flight, I'd want him to be very, very quiet ;-)
I'm gonna work hard to make them as loud and noisy as I can make them screem!!!
Funny you should ask this!! I was just thinking about how quiet my wife is when the kids are around but as soon as the kids are gone she could wake the neighbors three doors down (and we live in the country, half a mile from anyone). She is a screamer when there is no chance of anyone hearing us and I LOVE it!!!!!!!