I've been doing some reading on the 'net, and have heard of a way to 'silence' air pumps by doing the following - is this a good idea? -

1)Get enough matching 35mm film cans for each airline.Photo stores will happily give them away.

2)get some rigid tubing that is the interior diameter of your brand of airline tubing.For ordinary Penn/Plax tubing 5/32 works well,but check.

3)use a drill bit somewhat smaller than your rigid tubing to bore holes in the center of the lid and the center of the bottom.

4)Insert pre-cut lenghts of rigid tubing,top and bottom.Secure with super glue.

5)allow glue enough time to set hard.Usually this is a coupla hours.

6)once super glue is thouroughly set, use ordinary silicone sealant
on the insides, outsides and lid joints.Use lots and don't worry about neatness.(A nice fat rubbery joint is desired)

7)Allow silicone 24 hours to dry and cure.Cut short lenghts of airline tubing and push onto one rigid tube end.

8)install the silencer on each air pump outlet.

Thanks a lot

Air velocity and air noise are very, very low in aquarium pumps