Walls; Windows - Polycom RealPresence Group Series Reference Manual

Room Design and Layout
If we are, for example, in a room that is adjacent to a double-door entry to the building, then knowing this
we can take the inevitable doorway noise into account as we filter the sounds we hear both inside the
meeting room and coming from that adjacent entryway. Within our own physical and local environment we
have the ability to isolate local unwanted noise from local "sound of interest" (voices of other people, etc.),
and place the unwanted noise in an inferior position in our conscious thought pattern. We are able to do this
because we know where the noise is coming from and (usually) what is causing it. We may be annoyed by
the noise, but we generally are able to ignore it. As soon as we add conferencing to the meeting equation,
however, we add the element of electronic pickup and reproduction of all sounds. For the people at the
far-end, the unwanted noise is much more difficult (if not impossible) to ignore. They do not have the ability
to isolate it in three-dimensional space (the microphones eliminate the spatial reference) and they often do
not know what is making the noise. The brain of the far-end participant will devote more and more conscious
observation and thought energy to trying to work out these elements, in an attempt to isolate and finally
"ignore" the unwanted sound. We have already stated that they cannot do this, however, due to the
electronic separation between the locations. Thus they are left with an impossible task that takes up more
and more thought energy, eroding the perceived quality of the spoken communication over time. Frustration
and exasperation quickly set in, and the communication flow quickly falls apart.
This, then, is one reason we must pay even greater attention to the acoustic and visual issues for any
presentation space that will be connected via conference to another. Minor, seemingly insignificant
anomalies we often ignore in the local environment become significant impediments to smooth
communication with people at the far-end of any connection. In short, we must always ask ourselves, "What
does this look like and sound like to the people at the farend?"
In order to guarantee that the final conference environment will have a solid foundation, we begin with the
construction of the walls, floors and ceilings for videoconference spaces.

Walls

Conference room walls should be built from slab to slab. That is, there should be no gaps from the concrete
of one floor to the concrete of the next floor. Resilient, gypsum board mountings should be used to close
any gaps. The thickness of the gypsum board should be 5/8" or more (one layer of 5/8" and one layer of 1/2"
bonded together would be ideal) on the inside of the room, with 1/2" thick (or as required by local building
codes) appropriate for the outside of the walls. There should always be a difference in thickness between
the materials used on the inner versus the outer walls. That difference in thickness subdues mechanical
coupling (vibration) between the two layers. A good overall wall thickness is 6". It is recommended that
"offset stud" construction be used, typically a 6" header and footer with 3.5" verticals attached in an
alternating pattern one toward the outside of the footer, the next toward the inside and so on.
Fiberglass dense batting or mineral rock wool, 4" to 6" thick (the equivalent of R-11 to R-13) should be
placed in the wall space. The thickness of the batting is not critical. The critical aspect is that it must be
loosely placed in the wall space, not compacted to fit. The resultant wall will have excellent acoustic isolation
from the outside world. More significant acoustic isolation can be achieved by placing an additional barrier
layer within the wall space. Typically this barrier will be made of a dense polymer material, about 1/8" thick,
and the improvement regarding loss of sound transmitted through the wall will be roughly a factor of 10.
These materials are available from a variety of manufacturers.

Windows

Windows usually present the equivalent of an acoustic nightmare (as well as altering the way a camera
renders colors and brightness). They not only transmit room sound, but also allow unwanted outside noise
to intrude on the conference space. In the event that windows cannot be avoided, it becomes essential that
window treatment of some sort be used. This treatment should match the interior look and feel of the space,
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