Whenever you are in a situation where you share interior walls, floors and ceilings with another unit or house (semi-detached, townhouse, condo), you will hear some sounds. It is never 100% sound proof. Builders do ensure that shared living spaces are built to code to reduce the sounds coming from other units and from the exterior, however, in the middle of the night and early morning when it is most quiet, you will hear your neighbours more than you would during the day. Even in a single family home, you can hear outside noises, like when a car drives by with the radio blasting, you can hear the music resignate right inside the house. There really is no such thing as a sound proof home.
In a condo situation, people must respect each other and keep noise to a minimun during the evening, night and early morning. Normal, every day living should not present a problem between the neighbours. You just have to be prepared that you will hear some sounds when you live in a condo, townhouse or semi-detached home.