Carrier high efficiency furnace: at both high and low blower speeds hear a high pitched whistling noise from the heat vents in the rooms adjacent to the furnace. Cannot detect noise when doing a visual in the furnace room itself?

Check your return air filters. Does this system have zoning dampers? Make sure all supply grills are open. Some times duct tape can come loose and give a odd sound. You may have to investigate a little further to locate the or pinpoint the sound for us to help.