Strategies for Noise Control from Plant Rooms

First step towards noise control is to centralize major equipments. All rotating and vibrating equipments like chillers, pumps, generators and fans are contained in a common space instead of scattered placement. With centralized placement structural treatments to reduce noise transmission are easy to incorporate. Walls, floors and ceilings of central plant rooms are insulated accordingly to bring noise level down to desirable limit. Best location for pumps and chillers is basement level. Structural components at this level are heavy. For new buildings these are designed to take equipment static and dynamic loads. Densities of walls are selected to reduce low frequency noise. Heavy concrete walls are used for plant rooms. Doors in the walls are heavy gauge. These are kept closed and joints are gasketed.

Water circulating pumps are positioned on inertia blocks. These are concrete structures with 3 times the weight of pump motor set. Pump motor base channel is fixed on top of this foundation. Inertia block is isolated from floor and structure with high density cork sheet. Piping connections with pump discharge and suction side are isolated from pumps with flexible connectors. Inertia block dampens pump vibrations. Cork sheet prevents any noise transmission to structure.

Likewise chillers are placed on spring type vibration isolators. These isolators separate compressor and pumping movements from chiller foundations. Compressor itself is isolated from chiller machines. Chillers are selected with lowest noise levels and minimum vibration.

After structurally isolating all vibrations from machines, acoustic panels are used for noise control. Fiberglass sound insulations are fixed in cavity walls in central plant room. Heavy concrete wall is covered with this panel, and then protective wall is built in front of it.

Walls and ceiling penetrations for ducts, pipes and cables are a source of noise transfer to other areas. After crossing of these services, sleeves are caulked with sound proof and fire rated material. Vertical crossings of service shafts at each level are treated likewise. Access panels in the walls for these shafts are of heavy material with gasketed joints.

Air handling units at each level are placed at a location where sufficient space above ceilings is available on minimum two side walls of the room. If it is located at a place where adjacent walls are lift well or staircase, ducts cannot pass through these areas to serving zones. Less space will require high velocity ducts. High velocity duct is a source of noise for public areas. When sufficient space for supply and return ducts are available on adjacent walls, ducts are designed with low velocity. Low velocity ducts don’t cause any noticeable noise while crossing public areas.