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Building design standards and guidelines typically contain requirements for maximum background noise in occupied rooms due to heating, ventilating and air conditioning (HVAC) systems. Acoustic ceilings can conceal HVAC systems and attenuate noise generated by devices in the plenum. Predicting the amount of attenuation provided by a suspended acoustic ceiling is straightforward and described in the ASHRAE Handbook HVAC Applications by the American Society of Heating, Refrigerating and Air Conditioning Engineers and the AHRI Standard 885 by the Air Conditioning, Heating and Refrigeration Institute.