I had a 2215 and bought it because it was known for being quiet. For me, it didn't start out quiet, often had to turn the filter on and off to let the air out. Was it the same for your other 2215s?
After awhile the noise should stop - I think it's due to biofilm build up on the plastic surfaces and the impeller itself. If the impeller is brand new I suspect air bubbles will stick to it, like when my filter was new.
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