Washington County Schools completes HVAC sound study

Washington County Schools has completed a sound study of the new HVAC system at Daniel Boone High School following months of noise concerns from nearby residents. During Tuesday's Washington County Board of Education meeting, another local resident provided public comment about the HVAC system. Superintendent Jerry Boyd said the district recently completed a sound study in the meeting, and that the district is "sharing that document for public review and the public record." During public comment, local resident Kris Lowe brought earplugs to the meeting, saying wearing them has become part of her routine at home. "I can feel the vibrations of it while I'm lying in my own bed," she said. "Dinner on our back deck doesn't happen anymore. It's too loud … When it turns off, we both catch ourselves with a sigh of relief." The environmental sound study was completed Sept. 1 by Wingfield Environmental Inc. According to the report, all measurements were recorded using factory-calibrated Casella 63x sound-level meters. While Washington County does not have a general noise ordinance, the report included the City of Johnson City's noise ordinance for reference. Under Johnson City's ordinance, the maximum permitted sound level in a residential zone during the daytime, defined as 7 a.m. to 11 p.m., is 75 dBA. During nighttime hours, from 11 p.m. to 7 a.m., the maximum is 55 dBA. Measurements are taken at the property line or multifamily boundary, according to the city's legal code and charter. For the study, two sound-level meters were placed on either side of the chiller, while two were placed at each of two neighboring residences. Both instantaneous and continuous measurements were taken. Between 1:45 and 2:30 p.m., the devices took instantaneous measurements. When all three fans were running, readings ranged from 56 to 68 dBA across the locations. When no fans were running, background sound levels ranged from 46 to 51 dBA. Higher readings were recorded closer to the chiller, while lower readings were recorded at the residential properties. Continuous measurements were also collected Sept. 1. The meters measured both dBA and dBC, which use different weighting methods to account for how sound is perceived. The dBA scale is designed to approximate the sensitivity of the human ear and places less emphasis on low-frequency sounds. The dBC scale is flatter and includes more low-frequency sound, including bass. Continuous dBA and dBC measurements were collected at the Brock residence. No continuous readings were available from the sound-level meter placed in the Wilson residence's yard because technicians at the scientific equipment rental provider were unable to retrieve the continuous data from that unit, according to the report. Readings from approximately 8:32 a.m. to 10:32 a.m. and again from 1:42 to 4:12 p.m. were taken while one fan was running on the chiller. Readings from approximately 11:02 a.m. to 12:12 p.m. were taken with two fans running, while readings from approximately 12:22 to 1:22 p.m. were taken with all three fans running. The different operating conditions were tested to evaluate sound levels at various functioning capabilities of the chiller, according to the report. At the Brock residence, dBA readings ranged from about 58 to 71 dBA with one fan running, about 60 to 70 dBA with two fans running, and about 58 to 67 dBA with all three fans running throughout a 8:30 a.m. to 8 p.m. time period. The dBC readings ranged from about 84 to 97 dBC with one fan running, about 90 to 96 dBC with two fans running, and about 85 to 94 dBC with all three fans running. Measurements were not recorded during nighttime hours. The district previously approved plans to plant trees around the new HVAC unit to help reduce noise. The board approved the plan Aug. 4, with planting expected to take place sometime this fall. The district plans to plant 25 fast-growing arborvitae trees, an evergreen conifer in the cypress family. Board members noted that the trees' dense foliage could create a noise barrier within a year or two as they grow. The district said it will continue working with residents near Daniel Boone High School.