Polycom 2457-23216-002 User Manual
Integrator’s Reference Manual for the Polycom RealPresence Group Series
240
Polycom, Inc.
ambient noise level). A room built to the description found elsewhere in this
section will usually fall between NC-30 and NC-35. The actual NC value is not
section will usually fall between NC-30 and NC-35. The actual NC value is not
critical; what is important is that the room be built with the intent and care
required to achieve the low noise rating. Typically in architectural design, a
site evaluation and analysis are required to certify the noise performance of a
required to achieve the low noise rating. Typically in architectural design, a
site evaluation and analysis are required to certify the noise performance of a
given space. The quieter the room, the easier it is to hear others in the same
room as well as be heard by others who are participating via conference
connection to a far-end location (or locations).
Almost every conference room of medium to large size (larger than 12’x15’)
requires some level of acoustic treatment to provide good speech-rendering to
other conference sites. The quality differences lie in the areas of intelligibility
and consistency of loudness as presented to the far-end. While the people at
the far-end may hear the sounds coming to them, it may be hard for them
clearly to distinguish all of the vowels, consonants, inflections and nuances of
actual human speech communication. (We all know that it is not simply what
you say but how you say it—i.e., the inflections and intonations—that makes
the difference in perceived meaning in human communications.)
Good audio practice dictates that the treated surfaces be composed of at least
two nonparallel walls. And, as the VCS hardware is a potential source of
room as well as be heard by others who are participating via conference
connection to a far-end location (or locations).
Almost every conference room of medium to large size (larger than 12’x15’)
requires some level of acoustic treatment to provide good speech-rendering to
other conference sites. The quality differences lie in the areas of intelligibility
and consistency of loudness as presented to the far-end. While the people at
the far-end may hear the sounds coming to them, it may be hard for them
clearly to distinguish all of the vowels, consonants, inflections and nuances of
actual human speech communication. (We all know that it is not simply what
you say but how you say it—i.e., the inflections and intonations—that makes
the difference in perceived meaning in human communications.)
Good audio practice dictates that the treated surfaces be composed of at least
two nonparallel walls. And, as the VCS hardware is a potential source of
distracting fan noises, the walls to be treated should include the wall
immediately behind the VCS hardware, whenever this hardware is within the
immediately behind the VCS hardware, whenever this hardware is within the
conference room proper. To help prevent meeting audio from leaking into
adjoining hallways or offices, the walls along those areas also should be
treated.
Approximately 50 percent of the wall area needs be covered with acoustic
panels. The type recommended is 1” thick compressed, dense-core fiberglass,
fabric-covered, or equivalent, with a SABIN (sound absorption index) value of
0.9 average. This specification is sometimes referred to as NRC (noise
reduction coefficient). If reduction of sound passing through is required, then
adjoining hallways or offices, the walls along those areas also should be
treated.
Approximately 50 percent of the wall area needs be covered with acoustic
panels. The type recommended is 1” thick compressed, dense-core fiberglass,
fabric-covered, or equivalent, with a SABIN (sound absorption index) value of
0.9 average. This specification is sometimes referred to as NRC (noise
reduction coefficient). If reduction of sound passing through is required, then
an additional barrier layer is laminated to the dense-core material, usually
3/8” thick fiber compression board. The barrier layer is placed against the
existing wall material, then the acoustic absorption panels are placed on the
3/8” thick fiber compression board. The barrier layer is placed against the
existing wall material, then the acoustic absorption panels are placed on the
interior-room side of that. The barrier panels will have a SABIN of 0.9, but will
have an additional specification of an STC (sound transmission coefficient) of
20. STC is a measure of the amount of reduction in loudness of sound passing
have an additional specification of an STC (sound transmission coefficient) of
20. STC is a measure of the amount of reduction in loudness of sound passing
through the material. Having an STC rating of 20 means there is a factor of 10
reduction in the amount of sound passing through that material. A
high-quality conference room wall usually has an STC of 60 or more—that is,
reduction in the amount of sound passing through that material. A
high-quality conference room wall usually has an STC of 60 or more—that is,
less than 1/1,000 of the sound in the room leaks through the wall.
Room Lighting
The brightness of the lighting in a videoconference room plays an important
role in determining the far-end view of the meeting. When there are low to
role in determining the far-end view of the meeting. When there are low to
moderate amounts of light—20fc to 35fc (footcandles), typical office
lighting—the distance range of “in focus” objects (depth-of-field) usually is
lighting—the distance range of “in focus” objects (depth-of-field) usually is