I just found a rather easy way to silence the entirety of the system without reworking the plumbing in my tank. It was originally set up with a wet-dry, and the drip tray silenced quite a bit of the air that went through the lines. When I tried running plumbing straight into the sump I was getting a large amount of air noise. My tank is pre-drilled on the bottom in an overflow compartment so I didn't have the option of running a secondary line and trying to make that one full siphon. Instead, I ran a piece of tubing through the large drain going into my sump, and made the tube the full siphon. Not only did that cut down on the water, but the tube being inside the pipe gave the air bubbles something to adhere to, and were able to escape back out before making it to the sump. Combine the return with a ball joint, and you can tweak it however you like. Nothing fancy, but it was cheap and easy.