In the last 6 months, we've noticed a "whoosh" sound in our 13 year old house. The sound is similar to what you hear when you enter a building through a revolving door -- but it occurs at various times throughout the day when no one is entering or leaving. The house has a dual a/c forced air system, electric attic vent, and fireplace, but it doesn't seem to center in any one room. It is more noticeable upstairs where there are two bedrooms and a bath. Could it be leaking air ducts? We don't think we're haunted even though we live near a civil war battlefield *S* Thanks.