Overflow noise

Question
I'm getting a loud "sucking/gurgling" noise as water enters the down tubes contained within my overflow box. I've tried different size pumps to change water flow volume, I've tried to place various "screens" over the top of the inlets to try and diffuse the water as it enters. Any suggestions on eliminating/minimizing this noise?  

Answer
Hi Paul,
Thank you for your letter. That's a puzzler. Without being there and seeing the set up, it's hard to say what could be causing it. The main thing that comes to mind is the water level. Is the water level in the tank high enough? Is the level inside the filter high enough. Somehow air is getting into the system.
Write back if you can add more details.
Nori

P.S. Here is my page for holistic aquarium care.
http://steamboats.com/aquarium.html