This is a phenomenon known as quantum locking. Since bald men don’t have hair to keep their heads warm, their heads can get really cold and act like a super conductor. The bottle cap can levitate and lock into position because any change in positioning would change the flux lines and disturb the state of superconductivity.
Like with AC units, there are quiet heat pumps and loud heat pumps.
I would look online for reviews that talk about sound. Look for information about decibels and or sones. A lot of manufacturers publish that info.
You might also want to see if anyone has published anything about the sound your models put out. That way you have a baseline number to compare new unit specs to.