We have recently moved into a 10 year old house with forced hot air heat. Every time the heat goes on we hear loud rhythmic banging from specific sites off the major duct in the basement. This sound travels up to the rooms feeding off thes ducts. It is very annoying. We have not been able to determine how to stop it. Please advise.

Perhaps your problem maybe in the blower compartment. With the power off to the furnas see if you can move the blower wheel in and out or side to side, that would indicate you have a bad motor which could make the noise you are describing. You can also listen or touch the motor housing when the motor runs to see if it vibrates. Hope this helped. Glen