We have 2 Australorps and a Black Star sex link, all 18 weeks old (as of today, actually) and have had them for almost a month -- the 15th will be 4 weeks exactly. We live in an urban area with a lot that is .13 acres, and we're separated from our neighbors by just a chain link fence, nothing else.
None of our neighbors can hear our chickens when they're just doing their chicken thing, clucking to each other or making that 'Pip!' alarm sound, or even scuffling over a choice bit of food. In fact, one of the neighbors from 3 houses down just came over today and was surprised to hear that we'd had the birds for almost a month, she never heard them at all, even when the brats were shrieking about something scary coming near the coop (like, my husband, or myself!)
The neighbors directly next to us can hear the birds IF the birds are being exceptionally loud AND the neighbors are in their backyards at the time. They cannot hear the birds from inside their homes. Even my husband and myself can't hear the birds when they're in the coop/run doing their bird thing, and we're only about 30ish feet away, with open windows. I figure that's quiet enough
Most of the time, particularly during the summer, there is just too much other noise -- like lawnmowers, car stereos, and shrieking packs of 9 year old children playing in the alley, not to mention radios, sirens, or dogs -- for our hens to even get heard over everything else.
Also, our birds really are quiet, unless one of us approaches their coop, they just don't make noise, ever. They may mutter to each other, but that's it! No shrieking, no bawking, no hooting or crowing or any other loud noise. Just the occasional quiet cluck. All bets are off if they see a threat, but even then, they just do this sort of strangled, drawn-out hooting. They're so quiet I tend to forget they're out there, when I'm inside working or whatever.
I think we got lucky because the flock of chickens that ours grew up with were free-ranged on a hobby farm well outside any city limits and they learned from their elders -- there is absolutely no reason to make a lot of noise. The flock that taught our hens how to be chickens was so quiet they didn't even sing egg songs! I know this because one of their adult Australorps hopped in the nest box to lay an egg while we were there and there wasn't a peep out of her. Or from the other 3 or so hens that were laying at approximately the same time.
I hope ours *stay* quiet like this -- they haven't started laying eggs yet! We'll see what happens when we get that first egg.
(sorry for bringing this post back, but I really wanted to share our experience, limited though it may be)
Whitewater