Oh wow, most people will tell you BO's are among one of the quietest breeds. I have two and mine really are pretty quiet, although when singing the egg song they can be pretty loud for a few minutes at a time. Also, one of them is very entitled. If someone else is in the nest box and she decides its her turn, she will pace back and forth in front of it yelling at them loudly to hurry up. As soon as the nest box is free, the noise stops.
Are chickens legal where you are? If so, I would worry less about a little hen noise. You might try talking to the neighbors to see if it is bothering them as much as you think it is. It might be a case where you are either closer to or more sensitive to the noise they make than the neighbors actually are. If you are on relatively good terms with them, you might try offering them eggs every now and then, which will probably make them happier to put up with a little noise.