One of the most common troubleshooting issues people get once they setup their tank is noise coming from their overflow. The most common noise issues are constant gurgling or flushing noises. Flushing noises come from downward water pressure on the drain lines causing a syphon. Much like a toilet, syphons speed the draining effect of the pipes which drains the overflow in seconds. As soon as the water line is below the pipes in the overflow it draws in air which breaks the syphon and causes the flushing noise.
To combat this, the Durso, Maggie muffler and other methods were developed. These methods introduce air into the drain pipe to prevent the syphon from ever happening. The issue with this is it introduces the second most common noise issue, gurgling. Gurgling often comes from the mix of air and water running through the drain pipe and exiting in the sump. Another side effect of this is the accumulation of salt creep from the air bubble popping and misting salty air around the sump area.
Two new methods were developed that not only help with the noise found with the durso method, but also provide an emergency fall back, the Bean Animal and Herbie. These two methods utilize a full syphon of pure water with no air. This eliminates the gurgling noise caused by the air and increases the flow rate that can be handled by a smaller diameter pipe. In addition, they both provide an emergency drain in case the main drain gets clogged for any reason.
If you are having issues with drain noise look into the Bean Animal and Herbie methods. They are both quieter and safer than the durso setups and can be installed into most aquariums with at least two bulkheads.