Plumbing Questions? Ask a Plumber and Get Answers ASAP.
does this happen when any gas applyance goes on
and is it only in the winter
the gas valve on the furnace may need to be lowerd
try to shut the gas slightly as the unit is on and see if the noise goes away
DONT FORGET TO TURN IT BACK ON AFTER YOUR DONE DONOT LEAVE THE VALVE LIKE THAT THIS IS ONLY A TEST
the next thing is you say you have fles gas lines is this house new if so it is verry possible the gas line may be undersized