single cresteds don't tend to be very vocal, although they will sometimes vocalize in response to handling or something you are doing. i have a few that make a quiet whistling noise when they are nervous about being handled. males and females are vocalize before and sometimes during copulation. i have one enclosure with several adult females in it and i call them my cranky old ladies because they "argue" all the time, especially over the best spot in the paper towel tube.