My house snaps, crackles, and pops (hence, Rice Krispies)!! It's very disconcerting. I bought the house in July and did some renovation, including removing a wall and adding a roof-mounted HVAC unit with new ducting. Now, especially when the heater comes on for the day and then when it shuts off for the night, I hear loud cracks, pops, and snaps; loud enough to wake me from sleep. What might be causing this and how can I quiet my house down??