Nice that you resolved those problems by diplomacy (something which is not used enough in the World, I would say), but often those noise problems are big enough to demand different solution. For example, in two houses divided by common wall both neighbors were complaining they can hear clearly each other when speaking normally, even in the soft voice! Party with loud music was out of question. My sound insulation project brought additional 55 dB of attenuation, but it was relatively expensive. Other example - piano practicing problem demanded expensive "room-in-a-room" solution, etc.