I was just thinking about using a bunch of egg cartons to line the inside of my grow cabinet. This would act as an insulator and sound barrier. I could hang mylar over the cartons for light reflection. Anyone ever try this? discus
If you want to be really stealthy: Get an electronic ballast, pump filter bag, put felt pads under anything vibrating, also get the biggest carbon filter you can to be more quite and prolong fan life. I have found that buy doing these steps you can significantly lower operating volumes. I haven't messed with eggcartons before.