To eliminate noise and vibration transmitted to critical rooms in an HVAC system, what component should be placed between the duct and the fan?

• A. Flex connector between duct and fan
• B. Duct collar
• C. Vibration damper
• D. Insulated sleeve

Answer: (A)

The flexible connector between the fan and the duct is what’s used to isolate vibration and reduce noise transfer into the ductwork and surrounding rooms. This component acts like a cushion, absorbing the mechanical energy from the rotating fan so vibrations don’t travel straight into the duct system. It also accommodates small movements or misalignment and helps maintain an airtight seal when installed correctly. A rigid duct collar doesn’t dampen vibration, and a vibration damper or insulated sleeve alone doesn’t provide the same decoupling effect between the fan and the duct, so they won’t be as effective at preventing noise transmission.