So, we had our heating and cooling people to the house yesterday and they said the noise is not coming from the furnace. In fact, the noise happened when the gentleman was here and he said the noise is coming from outside. He suggested that it is coming from the capital beltway project. We live by the beltway. So last night when the noise was going on all night - I took a drive to the beltway and guess what??? Nobody was out there working. So I'm starting to come back to our PRV. Any suggestions?