I just finished building a new home and as part of the Energy Star rating transfer grilles were installed above each of the bedroom doors to allow air exchange when the doors are closed. The problem is that sound (and a small amount of light) pass freely through the vents negating all privacy of closing the door. I've read that I should install a baffle into the vents to allow air to pass through but deaden sound. I can't find any details for where I can buy this or what kind of materials I can use to construct it. Any advice would be greatly appreciated.