We have noticed what you say about some women being silent in clubs and agree that being 'in the zone' is probably the answer. Rose is usually very noisy, in fact if we're in separate rooms in a club I can always tell which one she's in when I'm looking for her, even through closed doors, by her noise. But when she's in the swing being a greedy girl she tends to drift off into what she calls her 'altered state,' away in a trance of pleasure, and just moans instead of shrieking when she cums.
On our first club visit, La Chambre, we were in the darkened room with the starry ceiling when a woman shouted "I'm cumming! I'm cumming!" and all the other women moaned as if in sympathy. It was all very erotic.
Men generally don't make much noise even when cumming, but it's nice to hear a groan or two of satisfaction when one does cum. After years of keeping quiet so flatmates, parents and children wouldn't hear, I now usually tell my partner I'm close to cumming - but they can probably work that out anyway - and make some noise when I'm there.
We do tend to be noisier when we're at our, and others' homes. When we do swapped sleepovers there's nothing sexier than being woken during the night by Rose moaning in another bedroom. Cue for me to wake up my bedmate and get her moaning too!