air handler can create substantial vibration and the large area of the duct system would transmit this noise and vibration to the occupants of the building. To avoid this, vibration isolators (flexible sections) are normally inserted into the duct immediately before and after the air handler and often also between the fan compartment and the rest of the AHU. The rubberized canvas-like material of these sections allows the air handler components to vibrate without transmitting this motion to the attached ducts. The fan compartment can be further isolated by placing it on spring suspension, neoprene pads, or hung on spring hangers, which will mitigate the transfer of vibration through the structure. Sound attenuators The blower in the air handler also generates noise, which should be attenuated before ductwork enters a noise-sensitive room. To achieve meaningful noise reduction in a relatively short length, a sound attenuator is used. The attenuator is a specialty duct accessory that typically consists of an inner perforated baffle with sound-absorptive insulation. Sound attenuators may take the place of ductwork; conversely, inline attenuators are located close to the blower and have a bellmouth profile to minimize system effects. Major manufacturers AAON Carrier Corporation (also makes Bryant and Payne brands) CIAT Group Daikin Industries (also makes McQuay International, Goodman, and Airfel brands) Johnson Controls (also makes York International brand) Lennox International Rheem (also makes Ruud) Trane Vertiv See also HVAC Thermal comfort Indoor air quality References Heating, ventilation, and air conditioning Mechanical engineering