I have a two zone heating system with a slight whistle noise in the air flow, when one heating zone is calling for heat and the other damper is closed. Both zones are quiet when the selected zone is reversed. I remember a TOH program that installed a bypass around a zone damper to reduce air flow noise, but I cannot find it on the TOH web site.
Re: Noisy Damper
Do you need to know how to do it or where to get it?
Just go to a local hvac supply store or google it on line there is a ton of info.
here is the link to TOH anyway