Septic system pump too loud
The possible result of unplugging it for hours is that the pump may lose its prime. If that happens, when you do plug it in, it will run and run without actually pumping anything. If left this way, it could overheat and be seriously damaged. It is relatively easy to restore the prime in the pump, but you would not want to be doing this every day. It would be annoying.
Building a sound barrier sounds like a better option.