Is insulation inside a duct for the purposes of the ARE 5.0 PPD exam a resolution for reducing sound/noise within a duct? I vaguely remember mike newman mentioning this in the old PPD videos, but do not remember if he mentioned it being a correct or incorrect answer. I understand that insulation inside a duct would be a bad idea in real life because it cannot be accessed, and can cause buildup of bacteria due to moisture. But, for the purposes of the exam, if we see a question similar to this - would we select insulation as an option for reducing sound in a duct or not?