Hello I'll assist you today.
The problem the coolant level most be low and causing the heater core behing the dash to make noise.
First let check the coolant level on the radiator make sure to check when the engine is cold, if the level is low top off and road test, after the road test let the engine cool down and recheck.
We need to know why the coolant is low, the next step is to do visual inspection under the hood also try to see under car for coolant leak. If you cant find any leaks and the coolant still leaking you may need to take to a mechanic for a coolant pressure test.
I need to you check the engine oil dip stick and see if the oil is like a milkshake, this is a indication of coolant getting in the oil. if this is the case you need to replace the intake gasket.
Let me know if you have any more questions.