In condo, apartment unit, your ceiling could be another one floor. nowadays people tend to complain upper unit make lots of noise like foot stomping, furniture dragging etc.

i know brick laying common, party wall is minimum require of 230mm or 9 inch in thickness, how about the floor and ceiling in between two floors, especially condo and apartment unit?

concrete density is also affecting noise transmitting. higher concrete density acts as a mass dampening and reduce the structural noise being transmitted to other unit. that is why when you are in some condo/apartment with good building quality, you found noise is minimal comparing to other condo/apartment.

should the relevant authority revise the requirement (for eg thicken the thickness of floor/ceiling concrete structure, higher concrete density must be fulfilled, adding hollow styrofoam to the structure) in order to cater the residential needs nowadays?

im not in engineering field but i am trying to understand residential structural design nowadays. 125mm (5 inch) concrete slab would be very thin for a condo/apartment floor or ceiling in my perspective. 5 inch thickness apply to landed like terrace house, it is fine.

from my understanding, hollow slab/wall is good to reduce mid to high frequency air borne noise in comparison to solid one with same thickness for eg 9 inch wall. but using hollow slab for a floor/ceiling in condo/apartment it could be a nightmare to users as most of the time upper unit is generating structural noise against the floor.