Screaming baby

So I wasn't really sure where to post this, I just need some advice on what to do..I live in an apartment building and the people who live under me have a 3 or 4 year old little girl. I've lived here for 2 years and have maybe seen her twice? I hear her screaming and crying CONSTANTLY like every single day, multiple times a day. It's not like normal screams either like she's screaming at the top of her lungs. It really freaks me out and I don't know if there's anything wrong going on. I'm just concerned and I'm not really sure if I have a reason to be or if there's anything even going on...what would you ladies do about this? If anything at all...