Some "neighbors" are so loud at late night..very often...

What a loudness!

Is that normal or not?

Sorry I don't deal with Myths unless it's busting them like the MythBusters.

When I lived in apartments, yes, it seemed to be.
Especially if you lived close to a university.

Living in the suburbs the neighbors aren't loud late at night.
Just their freaking ill trained dogs.
And the cats that the a-holes who got foreclosed on left behind to become feral, fight, and scream in random back yards.

Spose it depends on where you live, the country, a village or a town/city. The type/quality of your neighbourhood, which usually also defines the quality of the houses when it comes to sound insulation. And of course your neighbours in particular.
In a bad neighbourhood in a city it could indeed be quite normal, in a small village with decent ppl only it would likely be abnormal.

Where I live it's totally quiet at night, mostly during the day as well. You can literally hear a pin drop.

If they're having the time of their life under the sheets then sure, it's perfectly normal and I encourage it. Love is beautiful, as long it lasts.
I sleep with earplugs, just in case so ill-mannered a-hole decides to stomp down the stairs obnoxiously speaking loudly on his/her cell phone at 5am, as recently happened a few days ago when I forgot to put them in.

I believe it depends on the behaviors of the people in your environment, some are respectful and considerate of others and and some just don't have manners they don't care if they are disturbing the peace and quiet of the neighborhoods. In the place where I live in, everybody seemed mindful of their behaviors and they avoid unnecessary noise as some neighbors will report it to the building administrator and file a complaint.

Well, if you think they are too loud , it would be better to go talk to them in a nice way . There's nothing wrong if they are having a party or just enjoying but at least controlling their noise as to not disturb the others will make a harmonious neighborhood.

for the city? yes.. burbs? also yeah.. they can be loud at times.. the saying "can't choose your neighbors" is NOT a myth...

personally I got fed up of the 'noise & frustrations' from disrespectful peeps and got myself a place in the country.. the closest 'backyard' is about 1/4 mile away..

My neighbors listen to Led Zepplin SO FREEGIN LOUD!
Sometimes I even consider shutting my windows and turning my stereo down.