We bought our house 8 months ago. It's in a nice neighbourhood, reasonably quiet. Our next-door-neighbours are a "nice family". They smile and say hello, keep their house and garden nice. They have a son who lives at home who looks around 20 years old. He doesn't seem to work or go to college, but plays on his xbox/playstation a lot. He has his bedroom window (at the back of the house) open and, I'm not exaggerating, he shouts at the top of his voice! He's a big lad and it is so loud. They are Polish so a lot of the time I can't understand what he is shouting but sometimes he speaks in English and swears a lot. This morning I have repeatedly heard "ahhhh fuuuuuck!!!". It is really bad when you're out in the garden, so much so that we have found ourselves not really using it even in this weather. But you can also hear it from inside the house. It happens when his parents are home, but the volume gets even worse when they are out.
I am aware that I am not a particularly tolerant person, but even my partner who is extremely laid back is getting irritated by it. Would we be unfair to complain about this? Any advice on how we could go about it without causing bad feeling with our relatively new neighbours?