I live in an apartment. Above me is a holiday let. I dread the summer holidays when we are going to have families staying. About a third of the families you would not even know they are there, but the rest of them appear to let their children run and up and down screaming constantly, parents shouting at the kids, jump off furniture, furniture being dragged across the floor, hoovering at midnight, jumping off their bunk beds which is above my DD's room until all hours, it sounds like there is a herd of elephants about to come through our ceiling. It beats me also why come on holiday, and spend all day in an apartment with the kids cooped up? There is a beach literally 2 minutes away.
Being a reasonable person and a Mum myself, I initially give them the benefit of the doubt - if they don't live in an apartment normally they are not to know how loud they are to the people living below, despite the holiday let company putting information at my request into their welcome pack about being considerate to the people living below and around their holiday home. Initially I will go upstairs and ask them politely if they could stop whatever noise it is - their children running up and down and jumping off furniture, hoovering at midnight etc, as it is extremely noisy for us as a family who live in the apartment below, and have to get up early for school/work - I invite them to come down and hear it for themselves (none have taken me up on it). This is usually greeted with a blank stare, sometimes a shrug and a response along the lines of "but we are on holiday, what are we supposed to do?" "we've paid a lot of money to stay here, the kids are just having fun" etc. etc. and the noise carries on. Occasionally there is an apology and a clear improvement in noise levels. I past years I have made repeated requests to the people staying their with no improvement and if anything an escalation in the noise, probably to "teach me a lesson".
After four years of this, they now get one polite request. If they don't stop the noise levels we respond with some very loud anti social noise of our own, bearing in mind we get up at 6am for work, sadly that is the only thing which appears to get them to lower their noise levels and be more considerate. It is almost like because they are on holiday, so don't have to give a shit about anyone else and their kids just do whatever they want with no consideration for others. Sheer entitlement on the parent's side.
The example given however, of a distressed and crying teething baby, I would not complain about, and would feel sympathy for the parent and speak to them if I saw them in passing about whether they needed anything, ie calpol, chemist, GP etc.