Good Option for Soundproofing Ceilings in Flats - Resilient bar Ceiling system
Where you are constrained by height issues the choice of a resilient bar ceiling may be your only practical option when soundproofing ceilings in flats. This solution will lose just over an inch (35mm) from your original ceiling height.
The resilient bar, or sound breaker bar works by decoupling the new suspended ceiling from the joists. The new ceiling is in effect floating off the joists via lightweight corrugated steel bars. The sound is absorbed as it travels through the corrugated flange of the resilient bar.