As others have said, they're usually fairly quiet, but can get loud when doing what people call the "egg song". Some of mine get very loud and very raucous and it'll go on for several minutes. Your neighbors will hear them. I definitely second the advice to check with your local laws and regulations. More than once, we've had members get attached to their flocks like pets only to have to rehome them all with only a few days' notice. If you're not allowed to have chickens, you're setting yourself up for some heartbreak by trying to sneak them.
Just as an aside note, if you put a fake egg in each of the other two boxes, it'll encourage the girls to use them. I find that the girls want to lay their eggs where another hen has laid hers. If a hen sees an egg in a box, she figures that box must be suitable. I have 24 hens and 5 next boxes. They were all trying to use whichever box the first hen laid an egg in that day and then squabbling when that box was occupied. I put a fake egg in each box and now they'll lay in whatever box is vacant.
My 7 girls have 3 identical nest boxes lined up in a row. However, they all prefer the first one. Some of my girls can be their loudest complaining that someone else is in the nest box they want to use!
Just as an aside note, if you put a fake egg in each of the other two boxes, it'll encourage the girls to use them. I find that the girls want to lay their eggs where another hen has laid hers. If a hen sees an egg in a box, she figures that box must be suitable. I have 24 hens and 5 next boxes. They were all trying to use whichever box the first hen laid an egg in that day and then squabbling when that box was occupied. I put a fake egg in each box and now they'll lay in whatever box is vacant.