1. Rattling sound
Reason – When a panel is not tightly put on the gas furnace unit, you may hear this rattling sound because the loose panel is banging on the other parts of your gas furnace.
How to fix it – Just make sure no panels or screws are loose on the gas furnace unit.
2. Popping or pinging sound
Reason – The duct system associated with your gas furnace may expand or contract as it starts to heat or cool.
How to fix it – To mitigate this type of noise, you must fix the air ducts system.
3. Grinding sound
Reason – The grinding noise is associated with some type of broken parts in the internal system, most probably the motor bearing.
How to fix it – In this situation, don’t try to act like a know it all. Call the HVAC maintenance and repair guys or fix an appointment directly.
4. Squealing sound
Reason – This squealing can be caused by the belt that is connected the fan to the motor.
How to fix it – In such cases, a simple belt replacement is enough.
Read about the noisy gas furnaces here in this article here – How To Fix A Noisy Gas Furnace?