babies can't sleep because of neighbor's karaoke   

Oh, I have the same problem as yours. Exactly the same.
What I did was, I called up the guard of our subdivision and have them told that they (our neighbors) are not the only residents of the subdivision.
We also turned on our airconditioner and closed all doors and windows.

Call the police

Singing is a very good passion, but I think you are feeling the heat of it. I think you should go and tell them, the fact, what are you going to lose? They should understand these things, or maybe you can send them the link of this discussion, once they read these replies, they might repent.

i would talk to the neighbors an tell them what they are doing is keeping your babies up at night.{but tell them politely}an if that didnt work i would call the police an see what they can do to stop them from singing,there must be some kind of law were you live.good luck.

Talk to them first, they may not realize that they are keeping anyone up or that their music is so loud. If that doesn't solve the problem I would go over there, holding the awake crying baby and remind them to please turn the music down. After that if it continued I would call the police. Your town probably has some kind of noise ordiance that they are in violation of. The cops will probably come give them a warning first, hopefully that will solve the problem.

Many people just don't realize that what they are doing is affecting others, so I would first go and talk to them. Make sure you are polite about it, since you don't want to make enemies with your neighbors.

If that doesn't work, then you should call the police and have them enforce what ever local ordinances there may be. Most places have some type of noise ordinances. In my neighborhood, any loud noises are not allowed between 10pm and 8 am.

I hope that you can settle things peacefully. It's much nicer to have friendly neighbors than those who constantly battle with you.

Maybe you could discuss the matter with the other neighbors that live around you and have a talk with the people that are having the loud parties. If they don't stop their bad habits contact the authorities to see if they can do something about it.

try to talk to them about it first.and if they are still doing it call the police.