Is there such a thing as a silent pump for an indoor fountain?
If the pump in your fountain is making noise, you may not have enough water in the fountain. The fountain pump is a (small) aquarium pump, and it must be submerged to work quietly. But properly submerged, those things are basically silent. Fill it up, start the pump, then add more water until the sound goes away. The water level in the fountain’s resting state is higher than it will be when the fountain is running, since there is no water “in transit” when the fountain is at rest.