Thank you. Stealth has been a major part of my design. Though I'm always looking for more ideals.
You can't see in the images, but my air pumps are in there too. I've tried many ways to quiet them down as much as possible. Hanging them from cords, bungie cords, in a muffled box (over heats if you forget air holes), all kinds of things. But no what as the pumps start to age, they start humming louder and louder.
A solution (as it happens a lot) came about on accident. On the left side of the closet I've built some shelves. The middle one holds my humidifier, which blows across the top of the screen. Below that I put a small tub, I thought I might try for a passive cooling system. during the setup for this grow, I put my two air pumps on top of the tub. One of the pumps had been getting louder, so I figured the valves were wearing out. But now I couldn't hear it at all. I'm thinking that the tub lid is able to give just enough and absorb the vibrations. Sort of like a large drum, the frequency is high enough, but the wave size is small, so no noticeable vibration sound.
Though I need to keep an eye on that pump and switch out soon. Does anyone rebuild your pumps, or just buy new ones, or is there a good high quality pump that last more than a year? Or is there a better way to get lots of air into the tub? I've bought used pumps at yard sales, then replaced the valves. Just not sure if that is cost effective over the long run.
Prairie
I used to order new diaphrams from he manufactuer, but now I use those cheaper Dual Whisperer Aquarium pumps from Walmart. After three grows, still no nosie or vibrations, but I hang them from the cords. I use two 14 inch aquarium air stones.