Gurgling sound in sink when home heater is on

I don't think this is normal. The next time you hear it try cracking a window or door open(preferably near the furnace)a little bit and see if it stops.

I am going to guess you have a high efficient furnace? There is a condensate line inside the bottom panel with a trap in it. This line plugs up with what I can assume is dust and dirt from the air. Before it totally plugs up and causes the furnace to go into safety mode and short cycle and not light it gurgles.
Shut your furnace off and remove this condensate tube, cleaning it very well and you should be good to go.
I am guessing the sound through your drain is just an echo since the condensate drain for the furnace drains into the plumbing system.
Contractor John
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