Specifications

Integrator’s Reference Manual for Polycom HDX Systems
A–8 Polycom, Inc.
It is important to remember that the use of traditional meeting room
downcans—even those that have color-corrected light sources—for any
lighting in the field of view that may include human faces is to be avoided at
all costs. These will result in extremely uneven fields of light, or pools, and
heavy, unnatural shadows on the faces of the participants.
Room Preparation Conclusion
When we follow the above guidelines we dramatically improve the odds for
success in the final deployment of live bi-directional conference-based human
communications. An added benefit is that this approach dramatically
enhances the effectiveness of the room as it operates for more traditional
meetings and presentations. The environment is more comfortable and
flexible, and less dependent on specialized electronics for “fixing” deficiencies
in the environment.
Audio Elements
Once the space is prepared, we can focus on integration of the various
audiovisual tools within the environment: audio, video and control.
Audio Input
The primary input device for the audio portion of any conference system is the
microphone. Elsewhere in this book [Basics of Audio and Visual Systems Design]
we have discussed how these devices operate within a given acoustic
environment. We turn now to a short discussion of how these elements
operate within a conference environment, where such factors as
“three-to-one” rules and “critical distance” often are pushed to the limit or
violated entirely.
When sound travels in a room, it follows “the inverse square law.” This means
that the sound level heard at a microphone drops by a factor of four every time
the distance doubles. Another important consideration in room audio design
is the concept of “critical distance,” or the distance at which the loudness of the
room background noise plus reverberation is less than one tenth of the
loudness of voices getting to a particular microphone. (This definition is the
result of research conducted by Don and Carolyn Davis. that is referenced in
the chapter “Designing for Intelligibility” in the Handbook for Sound
Engineers.
1
)
1. Davis, Don and Carolyn. “Designing for Intelligibility” in Handbook for
Sound Engineers: The New Audio Cyclopedia, ed. Glen Ballou (Indianapolis:
Howard Sams & Co., 1991), 1279-1297.