Too much sound — particularly from HVAC mechanical systems — can be a problem for productivity in commercial buildings.
At industrial equipment manufacturer Mi-T-M’s 68,000-square-foot office headquarters in Peosta, Iowa, high ambient sounds from its mechanical air-handling units made it difficult for employees to have conversations in person and over the phone.
“After our first month, we decided on somehow abating the mechanical noise,” said Thomas Allendorf, managing director of operations at Mi-T-M.
A solution was found by using fabric duct for air distribution — an HVAC construction alternative material preferred by Mi-T-M’s CEO A.J. Spiegel for its aesthetics and installation labor savings when compared with metal ductwork.
But finding a fix took a while. Enter Michael Wuertzer, Mi-T-M’s plant maintenance supervisor, who — with a little innovative thinking — tried to attenuate the mechanical noise by lowering air-handling unit airflow by 60 percent with the unit’s built-in frequency drives. But when the noise still wasn’t reduced to acceptable levels, Wuertzer and Allendorf had local fabric duct manufacturer DuctSox Corp. develop what it said is the world’s first fabric sound attenuator for fabric air-dispersion systems.
DuctSox’s dBSilencer is 48 inches long and 30 inches wide — 8 inches wider than the fabric sound attenuator’s accompanying 22-inch diameter duct, which accommodates the 4-inch-wide double wall of rock wool. The attenuator also offers an optional bullet centerpiece. It’s available in diameters ranging from 12-30 inches and is installed in-line where the inlet of fabric duct meets the connecting metalwork duct from the air-handling unit.
The dBSilencer was tested by Intertek Labs in Cortland, New York, using a standard laboratory measurement of acoustical and airflow performance of duct liner and prefabricated silencers. Lab findings revealed that the fabric attenuator with a center bullet sound absorber was as equally effective as metal sound attenuators in dynamic insertion loss up to 500 hertz and more effective than metal in the 500-8,000 hertz range.
The fabric sound attenuator was also beta-site tested at Mi-T-M’s offices, where noise levels dropped 15 decibels, representing a decrease of more than 50 percent, according to Wuertzer.
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