Vertical transmission of vibration and noise to a research laboratory from mechanical equipment room - analysis and mitigation case study

摘要

A newly occupied large public university research building received floor-vibration complaints from a laboratory located above a mechanical equipment room. Researchers, who observed surface ripples in water glasses on lab shelves, investigated and found interference in floor-mounted specimen incubators. Structural vibration and low frequency noise can effect sensitive laboratory equipment, degrade experimental specimens and reduce staff efficiency and productivity. Investigatory observations and measurements were undertaken during business hours to determine vibration and noise conditions and develop a plan of mitigation. Measurement results were compared to permissible 1/3 octave Vibration Criteria (VC), which had been used for building design, and prominent narrow band (discrete) frequencies were compared. Central plant equipment, including pumps and compressors are on ground level. Chilled water pipes from remote campus chillers are suspended in a crawl space below. Building air handlers, exhaust fans and boilers are in a penthouse equipment room and on roof. Structure borne vibration and airborne noise may be transmitted to laboratory spaces via building columns and beams, in pipes and ducts and through vertical duct and pipe shafts. Results are graphically shown on charts. Mitigation measures implemented by the facility management are enumerated with subjectively determined results.