If I get it right, when you approach the end of a page, you need to turn it, which creates unwanted noise.
To counter or eliminate the noise here are a couple of scenarios. They are like a blueprint and any of your solutions should fit the scenarios characteristics. Think of guided creativity.
It's ok to combine ideas mentioned and to develop them further.
Here we go.
When approaching the end of the page, by some means X you can completely keep TURNING away from any page, so there is no noise.
Idea: An X with this property could be e.g.
distributed pages. I.e. one set changes after odd pages, a second after even pages. If you split those sets among each other every choir member can follow left or right on leadsheets AND turn his or her sheet at different times, reducing noise considerably.
You modify the end of page such that there no longer is a need to turn a page, so there is silence.
Idea: You could take the one of sc.1 a step further and
break pages not only at the end but say
with an offset of half a page etc.
The end of a page is approaching and you can't prevent to turn it, thus creating noise, BUT X completely compensates the turning process' noise creation.
Ideas: The 3 ideas
Aaron mentions fulfill these properties. I.e. experiement with different
materials (noisy ones, silent ones),
turning techniques (noisy and silent ones) etc. Consider going
from uniform (all have the same medium, creating a lot of collective noise)
to non-uniform (mix of media for the same song with different noise creation).
Modification: Come up with a turning strategy which simply
spreads the noise in time. I.e. some start turning earlier than others, some later.
Sidewalk: When will the turning be most noisy? When you hold it up against the microphone. When will it be almost silent? Far away, lowered to the ground (i.e. shielded by the choirs bodies). Develop on that
X would be the
position, where you perform turning the pages.)
There are even more things you could do.
Resist the temptation to say "it's impossible, too costly" etc. Instead review what you already DO have (e.g. people, material, methods, rules, ...) and try identifying X amongst them (already there, or almost freely available).
A simple list, held against the 3 scenarios mentioned, might do the trick.