You can't use that setup with sump system it is designed for a closed loop type setup.
You should be able to silence your overflow, if you can give us some details on your setup we can probably solve the noise issue. Some things you can look at also if you have a drilled tank (internal overflow) look up durso stand pipes, and if you have a HOB overflow look at the Stockmans overflow and the Gurgle buster. All of these are DIY designs and very simple and inexpensive to build.