Hi - I'm in a new home and turned on the furnace for the first time - a Lennox Pulse 21, fairly new by the looks of it. It was inspected a few weeks ago by the home inspector and passed, but I didn't notice anything at that time. When the unit starts up, and begins blowing heat, there is a noticeable hum in certain parts of the house. I don't know if it's the motor, or some resonance in the ductwork (and can't even be sure when standing right next to the unit - I'm afraid to run it with the panels off). Upstairs, the sound of a television or stereo pretty much masks it, but it's there and it's bothersome. On the other hand, this house has two cold air returns, and heats up much faster than my prior home. Right now, I'm awaiting it to kick on again, and depending on the insulation, perhaps the unit won't come on that often or that long to make this a real issue. I live in the middle of Ohio, so obviously there is a significant
Winter. Any advice or help appreciated - thanks.

That's the sound it makes when its working right. That's the reason they call it the lennox pulse, It makes a pulsating noise while air moves through a diaphragm into the burner area. You can quite it down by adding a flex connector to the supply and return air duct. It will help the noise from transmitting through the duct work.