How loud is your acid pump?
I have nothing to compare it to, so I'm not sure how loud it should be. I have a Pool Pilot TC system with acid tank. The pump, when running, has a very loud hum to it. It seems to be working fine, but I can hear it inside my house through many walls. I hear it in the middle of the night and at all hours whenever it runs. It is only for a few seconds, but I can imagine my (close) neighbors are starting to dislike the noise. It's louder than my filter pump.
I have the tank set down on brick pavers, and it is in a 3 sided enclosure. Two sides of the enclosure is lattice with the holes in them. Only the back is plywood. Could it be that, or is the pump really that loud? It has always been the same volume.