CONTROLLING NOISE IN CONFERENCE ROOMS
Attention to acoustics in a Conference Room is extremely important in providing a meeting space that is both acoustically pleasant as well as functional.
Acoustic treatment of a conference room must do two things:
- Confine sound within the room so people on the outside cannot hear what is being said on the inside.
- Create a good acoustic environment for conversation both within the room or on audio devices such as speakerphones.
The first step is to insure that sounds transmitted outside the room are not permitted to transmit into the room. Common walls should be constructed with an STC of 55 or above, and should extend all the way to the structural deck above. High STC ratings can be achieved through the use of vinyl noise barriers and resilient isolation clips which add additional mass to the partitions as well as decouple them from the studs reducing both airborne and structure borne noise. External sounds can come from any direction so floors and ceilings must also be of sufficient mass to block noise. Sound inevidably will transmit through the rooms weakest structural elements which are doors, windows, and electrical outlets. Acoustically rated doors and windows are ideal, but the STC of existing doors can be improved with the installation of acoustical door seal kits, and the STC of existing windows can be improved by insuring that seals are in good condition and adding additional panes of glass with an airspace in between. Electrical outlets can be sealed with fire rated putty pads.
Heating, ventilation, and air conditioning systems are a typical source of unwanted noise and their design and location should be considered prior to construction. Air handlers, VAV boxes, and fan-coil units should never be located above a conference room. Ducts should be of sufficient size as not to produce high air velocities. Air handlers should be selected with low sound level ratings, and diffusers should have an NC rating of 25 or less. Acoustic duct liner can be used to absorb fan noise and prevent low frequencies from transmitting through the duct walls. Acoustic duct silencers can be installed to further attenuate fan and mechanical noise, and to eliminate crosstalk between spaces sharing common ductwork.
Hard surfaces in the room such as walls, ceilings, windows, floors, and tables all reflect sound creating a reverberant space, making speech intelligibility difficult. By adding absorptive materials to the walls and ceilings, sound is prevented from bouncing back and forth creating a comfortable speaking environment. Fabric wrapped acoustic wall panels, ceiling clouds, stretchwall fabric systems, and acoustic ceiling tiles are all excellent products for both absorbing sound and providing pleasing aesthetics.
To insure speech privacy, the installation of sound masking in areas outside the conference room is recommended. Sound masking, sometimes referred to as white noise, works by producing a unique, digital broadband sound spectrum complimentary to the speech spectrum, that effectively covers speech levels. This scientifically engineered sound is amplified through special individual speakers installed above the dropped ceiling, creating a uniform field of sound ensuring temporal and spatial uniformity.
Noise Criteria, (NC) is the measurement of how quite a room is with the HVAC running and no occupants in the room. All of the previous mentioned considerations contribute to the overall NC rating of a room. An ideal NC rating for a conference room is 35dBA or below; anything higher will begin to interfere with speech intelligibility.