I have read that Guineas are more noisy their first year.
I do know from having them, they make most of their noise when alarmed and at dusk.
They are quiet after dark so they don't bother anyone trying to sleep.
For some reason guineas seem to be louder then roosters up close, especially a bunch of them,
but the sound from a rooster crowing seems to carry further.
In New England the biggest danger to a guinea roosting outside at night is probably from Owls. During the day, they are in danger from the same predators as chickens, but can often fly up out of reach.
oh, and a guinea and chicken cross should be sterile.