There is no USA Volleyball rule or policy that states the game of volleyball has to be played in a quiet environment.  Participants and spectators can make as much noise as they wish during a match.  If you ever watch an international volleyball match (Olympics or other high level event) you will see an incredibly loud environment in the stands and on the court.  Many countries have fans that stand the whole time, chant, beat drums and sticks, etc.  The participants can hardly hear themselves or the whistle in such environment.  And the International Governing Body , FIVB, encourages such fan interactions.
We can understand the desire to not have distractions during a match, but the reality is, it is actually part of the sport.  Players will need to be able to adapt and be prepared to play in loud environments.  As long as participants and spectators are not yelling inappropriate things directed at individuals, then talking, chanting, making noise, is not an offense that can be sanctioned.  Yelling “Balls up” no matter if it is useful to them or not, is not something our officials should be stopping.
All involved with Youth Sports should, however, remember that we are trying to promote Good Sportsmanship at our events.  Parents and spectators should review the Parent Code of Conduct before each event.  Yelling excessively from the stands before the opponent serves may not be "demonstrating positive support for all players" if your motive is to distract/cause errors.  Please consider the good of the sport and good sportsmanship whenever you are cheering at our events.