You need to install double or triple paned windows and insulation. Windows are not easy to shortcut, but insulation generally is. Carpet is an outstanding sound deadener. I know other parts of the world have different construction and higher quality than American toothpick and plaster board crap houses. If you can access the spaces in the walls and ceiling, you can use old carpet instead of premade insulation. Even if you cannot access and install properly, you can line a room with carpet on all sides. You really need 2+ layers for some serious sound deadening.

I used to play in a band with a drummer that lived in a condo with neighbors all the way around him, above and below. He had a bedroom with a layer of carpet in the attic, another layer on the ceiling, and three layers of carpet on the walls and door. The space felt tiny, but he could practice as hard as he played normally and you could not hear a thing from outside the house. Inside it was no louder than people having a quiet conversation in the room next door.

I lived in Georgia at the end of a military base where they make the F22. When they do the first test flights of each plane, they took off and went vertical straight up above my house. It was so loud, you could not have any kind of conversation when it happened. Inside my house, it was nearly completely silent. The houses in the area all have triple paned glass and the wall insulation needed to make the sound irrelevant.

It is possible to hack a solution (carpet), and to quiet even the most high and low frequencies too. There are proper ways to do this that are more aesthetically pleasing. If you’re having mental health issues, hack something together with carpet. People throw away tons of the stuff all the time. The vast majority of carpet that gets thrown away is nearly brand new. It was under furniture or in closets and other areas of low to no traffic. Call up local construction small businesses or just find work sites with dumpsters. You’ll find some for free with a little persistence.