funny gurgling behind the dash

Hello,
My 93 Olds Cutlass Ciera 3.3 litre 212000 miles auto trans with air has begun making a strange gurgle that sounds like it is just behind the dashboard. It is most noticeable when the engine accelerates. The heat/ac can be on or off but the sound is the same. I could not hear it from outside the car with the hood open. (It will do it even if the car is in park and you rev the engine.) Any thoughts on this?

Thank you!

Air in your coolant system..
Is there air in your radiator?

Bass

I agree with Bass, that it sounds like air in the cooling system, and it's gurgling through the heater core. The most likely areas for air intrusion is a faulty water pump, loose hose clamp, radiator tank seam, or worst case, head gasket. Also, if you recently replaced any cooling system component (like a t-stat or hose), you need to bleed the system of air.