All of our broodies hatch in the coop, some in the 'broody area' which is simply the people entrance area which is separated from the chicken part of the coop by a wood framework with chickenwire on it. So the birds are routinely exposed to all of the noises within the coop. Just this past season we had 4 broodies in the 'broody area' which is 3.5 ft by 12 ft., there were 2 hens on either end (hens #2 and 3 on one end on the floor, hen #1 on the floor on the other end and hen #4 on the same end as #1 but up on a shelf 3 ft off the floor). Hen number 1 hatched while hens 2,3 and 4 were on various stages of their egg setting. Although the non-hatched broodies did watch hen #1 and her brood with great interest none got up off of the nest to interact. We did put a fence panel up so that the little ones couldn't run into the nests of hens 2 and 3... When hens #2 and #3 hatched on the same day they ended up raising their babies as a combined clutch... but again, hen #4 was able to hear and watch, but didn't leave her eggs. This was the most 'crowded' we have had it, but last spring we had 3 hatch within about 3 weeks of each other and it was similar... although all of the broodies were able to hear the new chicks none left their own eggs to interact. Though they were intensely interested in watching (But then again, after 3 or 4 weeks of setting they were probably bored stiff and just enjoyed the break in the monotony! ) and last fall 2 hatched within 2 weeks of each other and it was the same. This has repeated time after time with the same results within the coop... but..every coop and every broody are different! I have never brooder raised chicks in an area near a broody though, so if the chicks vocalizations are somehow different in a brooder than with a mama hen then there is always a chance of another reaction. Observation will be the key and I am interested to hear is you have a different result than we have with ours.