The range of sound basically reaches as far as the space is open and it can travel through air (over-simplification). If you put anything between a sound emitte

The range of sound basically reaches as far as the space is open and it can travel through air (over-simplification). If you put anything between a sound emitter and the receiver, it'll block out (some) sound. If that anything is made out of sound-absorbing material (something soft basically, again over-simplification), it'll absorb even more sound. The principle behind cubicles is to reduce the amount of open space immediately around you, with sound-absorbing material so both the sound you emit, and the sound others emit, travel more upwards than side-ways as the cubicle walls force the sound up, essentially making the environment more silent, if you are situated in a cubicle. If you were to be hanging from the roof above all cubicles, you'd get to hear basically all the sounds coming from the cubicles. It's a pretty basic solution, something better would be actual private offices where everyone is enclosed fully, then you can make the environment really quiet. But that's also way more expensive and requires more space.