Diagnosis
Debris (dust, pet hair) is caught in the fan blades, or the fan bearing is starting to fail.
How to Fix It
Power off and unplug. Use a can of compressed air to blow short bursts into the ventilation grilles on the back and bottom. Tilt the unit to help dislodge particles. This often clears the noise immediately.
If That Didn't Work
The fan motor itself may be faulty. Listen closely—if the noise is a consistent rhythmic grind, it's likely a hardware issue. You'll need to contact Samsung support for a repair or replacement.
Heads Up
Avoid vacuum cleaners directly on the vents, as static discharge can damage internal components. Compressed air is the safe method.