What are the various sources of sound entering an office and what can be done about them?
If the separating wall does not extend all the way to the roof decking it is a major source through which noise will be transferred. A wall like this will need to be extended to touch the roof decking and then sealed with acoustic sealant.
Sound travels through ductwork much of which can be reduced by installing sound baffles and duct liners. With increased mass, sound transfer is significantly reduced.
Cracks in doorways are another source of sound which can be minimized by installing weather stripping.
Acoustical tiles are also very effective. Tiles are now available which absorb sound from within and outside the room. Finally a dividing wall which is not airtight will inevitably transfer sound.
Effective soundproofing can sometimes be a problem in buildings despite the range of soundproofing materials available. Sometimes sound is conveyed through unexpected routes and finding a solution is a considerable challenge. When faced with a soundproofing question the best way to find an answer is to consult an Expert.