Diagnosis
That's usually normal operation noise from the refrigerant cycling, but if it's new and very loud, it can mean the unit isn't level or there's an air bubble in the coil.
How to Fix It
First, make sure the unit is on a perfectly flat, hard floor. Use a small level on top. If one corner is even slightly low, it can cause the refrigerant to drain unevenly and get noisy. Adjust the feet if you need to. Second, check that nothing is blocking the air intake or exhaust grilles on the back and sides—airflow is key.
If That Didn't Work
The noise might be coming from the water drain system. Check that the drain hose, if you're using one, has a steady, downward slope with no kinks or high loops that can trap air and cause glugging sounds.
Heads Up
A steady hum or fan noise is normal. A loud, intermittent gurgle that wasn't there before can indicate a developing issue with the sealed system, but it's rare. Give it a day of operation on a level surface; it often settles down.