i got that, because AK-47 is such a stinky strain and you never know where sarcasm's gonna pop up
i saw someones posting about how to make a homemade scrubber for around $25 i think....look it up
if you already have a box fan, and don't use really smelly strains, just get a $10 furnace filter with carbon scrubber and bend it's frame to fit the back side of a box fan and cut two pieces of cardboard to fill in the top & bottom voids, and just strap the filter to the frame and tape the edges off. that's what u used to push the warm air out of my 400w in my first grow.
any way you can get air to move through fish tank activated charcoal without letting dust out can be done to make a DIY filter.
if you're a woodworker, you could make a heavy wooden box with your blower inside and noise from that contained, with a second soundproofed air chamber blowing up through a screen with floss mats top and bottom to contain charcoal dust for a combination carbon scrubber and muffler if noise is an issue as the wooden air chamber would contain much of the air noise and the charcoal would diffuse the turbulence and a lot of the sound i bet.
i found just blocking the direct flow out of my blower with my hand playing around cut noise in half. i bet something like loofa would make for awesome diffusion mufflers.
it seems most people get so obsessed with cubic feet per minute that they don't account for noise which is always a problem for those with intrusive neighbors from hell that you can't miss any time you throw something up in the air. you don't need to move a million cubit feet of air per second to keep your room cool unless you're into the mega watts. just that simple box fan scrubber moved enough air out of my 400w halide (cooler than sodium too i bet, besides offering a fuller spectrum) so that i got a gentle breeze of slightly warm air out of my duct.
i think an impeded for muffler effect and carbon scrubbing design should be able to move enough air to keep a room cool as even impeded, a real duct fan would move many times what my passive blowing into a funnel box fan did, and my fixture was always just slightly warm to the touch.
it's like heresy to suggest anyone cut CFM for any reason, no matter how much it might actually be needed. if your neighbors are such assholes that any kind of fan presents problems, then a restricted one that's silent is best... deal with it. LOL
one of the luckiest growers i've ever seen had access to an unused spare room in a huge factory! i think he ended up using a door jamb ventilation system as there was virtually no circulation in the room. i myself passed up on an olympic swimming pool sized cavern loft because my would be room mate wanted me to give her an additional $50 a month for laundry so she could rent to own when $10 a month is more than enough for laundromats.
before i split, she tried to "give up" on the washing machine for the bigger better cut of the harveast deal *cha ching cha ching cha ching* once she figured out why i was so interested in the "attic space" and realized that gal would be nothing but trouble not to mention unbearable company to keep, but man, that wasted warehouse space was something to see as long as you didn't walk to the far end where the corner of the floor caved in a good 20 feet wide easily.
for a minute there, envisioned rows of 400w halide/sodium combos in the open air on light movers with soil mixing stations and hauled up water cisterns, but in my case, it wasn't about cha ching... it was about waiting 24 months for that old school grown as well as possible in 5 gallon buckets.