Wilson F.’s question answered:
That’s an excellent question and a very common occurrence, but very difficult to answer.
There is not a whole lot you can do, except asking the parent or guardian to try to calm the child. If that fails, then ask the flight attendant for help. If that does not solve the situation, we just must deal with it, trying to ignore the situation as much as we can.
Regs to protect passengers’ peace and quiet: It does not sound achievable. That sounds like a question for a lawyer or a law maker. Am afraid we are stuck inside that tube for the duration of any flight.