The use of conferencing equipment makes organizations more competitive, increases productivity, and decreases costs; audio and video conferencing technologies need to be accounted for in the construction of meeting spaces.
Acoustics
Audio is the single most important aspect of successful conferencing. To achieve quality audio, it's important to reduce reverberation and background noise. The way a microphone "hears" is different than how ears perceive sound. Sound reflections and background noise that may not trouble a local listener, when picked up by a microphone and transmitted to another location, can be annoying and may substantially decrease speech intelligibility.
Reverberation
Reverberation is the persistence of sound in an enclosed space after the sound source stops producing sound. This persistence of sound can mask speech and make it difficult to understand what's being said. Reverberation is decreased by surfaces in the room that absorb sound energy. Rooms with large areas of glass, concrete, metal ceiling deck, and other highly reflective surfaces are not appropriate for conferencing. Surface finishes in a conference center should include carpet, suspended acoustic ceiling tile, and acoustically absorptive walls.
Ambient Noise
To ensure intelligibility and minimize annoyance from ambient noise levels, the voice signal at a conferencing microphone needs to be at least 25 dB sound pressure level above the ambient noise level. Ambient noise levels are often measured or specified in terms of noise criteria (NC) curves. For the speaker's voice to be 25-dB above the noise level with typical microphone placement, the maximum recommended NC value is 30 to 35.
Mechanical systems for conferencing spaces shouldn't exceed this noise level. Noise produced by projectors, laptops, and other sources needs to be accounted for when calculating the NC value.
Noise Isolation
During construction, take special actions to reduce the amount of outside noise that enters the space. For example, the recommended wall construction for a conference room is a single row of studs with one layer of 5/8-inch gypsum board on each side (one of which is attached via resilient channels) and insulation in the stud cavities. Caulk the perimeter of each layer of gypsum board.
Technology Infrastructure
Millwork needs to contain conferencing microphones, network connections, power connections, and audiovisual control systems, and should allow for the inclusion of audiovisual interfaces for connection of computers to video-display systems.
Electrical conduit, raceway, junction boxes, and floor boxes need to be sized for the communication system's cabling and connectors. The diameter of cabling used in conferencing systems is larger than data network and telephone cables, and the connectors don't typically fit in standard electrical floor boxes. Space needs to be provided in ceilings for overhead loudspeakers.
Professional Help
An acoustic/audiovisual design professional is often required to ensure that nothing is overlooked. This individual generates specifications for the audiovisual and conferencing systems based on the owner's requirements. In addition, he/she generates specifications for acoustics, lighting, electrical requirements, and other infrastructure.
Scott Woolley is product marketing director, professional audio, at Salt Lake City-based ClearOne Communications Inc.
