To prevent you from being disturbed by the activity in the next room, whether the room is upstairs or in line, the construction has to prevent sound from being transmitted. This doesn’t have to be a massive concrete slab or wall.
Sound insulation relates to the overall ability of a building element or building structure to reduce the sound transmission through it. Two types of sound insulation might be referred to - airborne sound insulation and impact sound insulation. It’s important to keep in mind that the weakest link in the construction has a large impact on the total sound insulation. It’s e.g. very important to avoid leakage between construction elements.