If you want to stop sound passing between 2 rooms or offices, tradition dictates either build slab to slab or fill the space above the suspended ceiling with baffle block or similar fibre insulation. Spending much of my life with my head above the ceiling tiles I see it first hand – even if the acoustic insulation or slab to slab construction has been specified properly it is rarely installed correctly and if it is is won’t last for long. It’s usually nothing to do with the installer either (although I have seen rolls of insulation lying up their still in the bags!), it’s usually the guy who comes along after to do some wiring or something, and just pushes the baffle block (or whatever) aside or cuts a gaping hole in the gyprock. ITS HOPELESS!! It seems to have been long forgotten but, the reason why suspended ceilings were invented was for services, not filling full of fibre insulation. The remedy to this is so simple too. Rather than working around the services vertically (extending the partition to the slab) to block sound, use the ceiling.
OK, from the beginning: ambient or background sound level is the foundation on which partitioning design is specified. Usually delivered into a building in the form of air conditioning sound or external traffic sound it is unpredictable to say the least. Therefore, the sound blocking ability of partitioning has to cover a worst case scenario (or lowest possible level) of ambient sound. If the A/C cycles off or traffic stops everything goes quiet and the wall has to work hard to stop speech being heard on the other side. This is why so much effort is spent on the ceiling space.
So, the new way to deal with the old problem is to replace all that insulation and gyprock building in the plenum with a speaker which artificially (but very accurately) delivers a minimum ambient sound level into the space below. Oh, ‘white noise’ did I hear you say??Well, you would be right, but the technology has come on a bit since the 50′s. Adaptive Sound Conditioning as it’s now known is a highly sophisticated technology which if combined with a specific ceiling tile means you don’t have to put anything else in the plenum as the ceiling itself is now enough to stop the sound from passing over the top of the partition allowing the services and air to run freely. Now the best bit! Not only do you not have do anything in the plenum and simply build the partition floor to ceiling, you can actually down-spec the wall build to a less expensive rating (typically from say 45Rw to 35Rw)

This can simply be a less expensive stud partition or one of the latest demountable systems you can easily reconfigure.

Cost? Well that’s an easy trade-off. Substantial wall building and more costly installation labour for an end product that is inflexible, rarely even works acoustically VS guaranteed speech privacy, less expensive partition design, no baffle block etc less installation labour, easy reconfiguration and more is a no brainer.

Comments very welcome.