Next door's nanny is very shouty. I get that kids are stressful to deal with, and we all shout at them from time to time, but she bellows at them fairly frequently (and dealing with kids is kinda her job). I can hear a child screaming "I want my mamma" at the minute.
I'm not concerned the kids are in danger or there's abuse, but it's just unpleasant for them and I don't think I'd be happy if my kids were shouted at as often.
Would you mention something, or just keep out of it?