ERV ductwork sound transfer solution?

How to quiet ERV duct room to room noise?Mini Splut Heatpump, so no tying in. Main stale air duct line that connects the five rooms is 14ft long, with duct registers… How to quiet ERV duct room to room noise?Mini Splut Heatpump, so no tying in. Main stale air duct line that connects the five rooms is 14ft long, with duct registers…Read MoreGreenBuildingAdvisor