In building HVAC, what is the primary function of a duct attenuator?

• A. It filters air to remove particulates.
• B. It reduces sound transmission through ducts.
• C. It increases airflow velocity.
• D. It heats the air.

Answer: (B)

The main concept here is acoustics in ductwork: a duct attenuator is there to reduce sound traveling through the ducts. It works by absorbing and/or reflecting sound energy from the HVAC system, often using lined chambers, perforated surfaces, or packing that dampens noise from fans, motors, and airflow. This keeps noise from moving into occupied spaces.

It isn’t primarily about filtering particulates, so it won’t clean the air. It doesn’t serve to increase airflow velocity; in fact it can add a small pressure drop that designers account for in system calculations. It also isn’t a heater; heating is done by coils or heat exchangers elsewhere in the system. So the correct function is sound reduction through the duct, improving acoustic comfort in the building.