Noise Control for our purposes here refers to two subjects within a building: control of noise from heating ventilation and air conditioning (HVAC) equipment and room noise reduction.
In new facilities during planning and programming, overall system design is reviewed as well as placement of major pieces of equipment. The building structure is analyzed for its ability to insulate sound and vibration from noise critical areas.
Once preliminary equipment selections are made and sound power data is available the system noise is computer modeled and results are compared to the noise criteria goals for the spaces. Recommendations are then made for duct sound lining, silencers, duct transitions, and air terminal devices. A vibration isolation schedule is developed based upon the equipment and building structure.
In construction administration, we work with a balancing engineer to insure that air flow velocity goals are met and turbulence is reduced. In the commission process, noise criteria (NC) or room criteria (RC) design goals are verified and in some instances floor vibration levels are documented.
In problematic existing facilities, detailed noise measurements are completed; NC and RC values are calculated and compared to recommended levels. Existing vibration control devices are inspected and airflow velocities are checked. Detailed remedial measures are then presented for review and budgeting.
Room noise reduction involves introducing sound absorption to control the reverberant noise level in an enclosed space. Some examples of noise sources controlled in this manner are from occupants (multiple conversations at a restaurant, children in a museum) or from machinery. When levels in the workplace get above 85 dBA, OSHA will require that the owner institute a hearing conservation program. Bay Acoustics is often engaged to design solutions to lower reverberant noise levels below this threshold to avoid these costly programs.