Hoi Jürg
I recently bought the Game Zero, before that I had the Game One for 3 years. I had to change because the street noise (I live right next to the street) and the noise of my heating fans (I'm a Gfrörli) got on my nerves so much. And I can say that the Game Zero is insulating enough ;-). When you're playing or listening to music, you'll definitely have your peace and quiet, and you won't hear the pizza courier ringing. Remember that the sound is also a bit muffled due to the isolation, I was first shocked when I switched from the One to the Zero. But you get used to it. I haven't paid much attention to how it sounds from the outside, but I think there's a big difference there too.
Greetings