How can I make my aquarium setup less noisy?

There was a time when aquarium filtration was almost entirely driven by air pumps and many of us over a certain age still enjoy the sound of air bubbles rising in uplift tubes. The apparatus that produced these bubbles normally had rather optimistic names rather than the more honest 'Rattle and Hum' that better described them, and for the most part, these were devices that you hid from view and tried to muffle the noise. The advent of power filters largely changed all of this humming and bubbling however. 

Modern air pumps are far quieter than their older counterparts but the bubbles they produce are still noisy. Using an airstone turns this sound into more of a hiss that is easier to live with and decorative or supplemental aeration can be linked to plug-in timers that automatically turn things off when noise is likely to be an issue. Never turn off aquarium filtration in this way though.

The noise produced by power filters and water pumps is more likely to be a splashing sound, although Venturi outlets produce a hiss similar to that produced by an air stone. Unless your tank is particularly heavily stocked or home to species found in environments such as mountain streams, positioning the return so that the surface of the water is moving should ensure plenty of oxygen and eliminate the sound of running water.