In terms of duct attenuation, which statement is true?

• A. Reduces duct temperature.
• B. Reduces sound transmission by dampening ducts.
• C. Reduces sound transmission while maintaining airflow.
• D. Raises the noise level.

Answer: (C)

Duct attenuation is about quieting the path that air travels through without slowing it down. The goal is to reduce how much sound gets transmitted through the ductwork while keeping the airflow and system performance intact. That’s why the statement describing lowering sound transmission while preserving airflow is the best fit. Acoustic liners, baffled sections, and properly sized attenuators are designed to absorb or disrupt sound energy in the duct without causing a significant pressure drop or restricting the air.

The other statements miss key aspects. Reducing duct temperature concerns thermal conditions, not noise control. Reducing sound by simply dampening the ducts could unintentionally impede airflow or change system performance, which isn’t the intention of attenuation. And raising the noise level is the opposite of what attenuation aims to achieve.