Acoustical plenum barriers meet occupant expectations and comply with standards

Can I just use a full-height wall?

Yes, absolutely. In fact, most acoustic standards in the U.S. either require or prefer the use of full-height partitions sealed airtight. That will definitely work. But ask yourself if you are over-designing. The goal is to match the sound-blocking capacity of the partition below ceiling level with the sound-blocking capacity of the architecture above the ceiling level. The overall isolation is only as good as the weakest link. 

While the ceiling is not sufficient as a sound blocker by itself, it is not completely useless. The ceiling can provide about 20-25 points of sound blocking. If you extend your STC 45 partition full height above the ceiling, the noise has to transmit through the ceiling, through the upper wall and back through the ceiling in the adjacent room. That path is much more robust than the path directly through the lower portion of the wall. While full-height walls are the right way to go from the performance and compliance perspectives, you may be adding unnecessary costs in some cases. 

The guiding rule is that if the sound-blocking requirement between rooms is 45 points or less, plenum barriers should be seriously considered. Plenum barriers, when combined with a stone wool ceiling, can provide up to 50 points of sound blocking. This is also where full-height walls should be considered equally with plenum barriers.

Once the sound-blocking requirement exceeds 50 points, full-height walls should be used instead of plenum barriers. For example, Canada's Workplace 2.0 Fit-up Standards requires plenum barriers for standard offices, meeting rooms, training rooms and quiet rooms to achieve enhanced speech privacy. It's not until rooms, such as executive offices requiring secure speech privacy, that full-height walls are specified.