Jeez, don't joke about calling in the social services. It can be distressing listening to children crying, especially if you don't know the reason. Maybe it would be worth keeping a diary for a week. Are you out all day at work? If you are, you can't say they scream all the time as you are not there all the time. If after a week of diary keeping you feel there is real cause for concern, then approach the parents first. My friend had social services called on her when she was doing 'controlled crying' to get her young child to sleep at night and it is not a pleasant experience.