A quieter alternative to the traditional box fan for a #CorsiRosenthalBox is to mount 5 or 6 Arctic P14 PST computer fans under a piece of cardboard/foam core/poster board instead. (They come in 5-packs.)
It can increase the initial cost a bit, but I feel the ability to comfortably run the unit 24/7 makes up for it.

To power the fans, you need a 12v fan power supply like this:
https://www.amazon.com/dp/B0BBSBV9CF

Mounting screws should be #6-32 x 1-3/4" with #6-32 hex nuts and optional #6 washers.

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If you want to cover the PC fans to keep little fingers or paws safe, you can use PC fan grills, baking tray grills/cooling racks, or gutter guard mesh.

Also, I recommend getting the tallest filters you can, 20"x25"x1" or 20"x30"x1", because the greater the filter area is, the longer they last and the less they restrict the fans' airflow. At Costco, they're even the same price as the smaller 20"x20"x1".

PS: painter's tape works as well as duct tape while being less sticky to work with.

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PPS: if you're in the US or Canada, the least expensive source for the Arctic P14 PST 5-pack is Amazon:
https://www.amazon.com/dp/B07HC782D5/

It's cheaper for Canadians to order from that link and pay the additional shipping fees than to order them anywhere I've found in Canada. Same is true of the 12v fan power supply linked upthread.

Costco.ca has the Filtrete 2200 in a 4-pack, Costco.com has the Filtrete 2500 4-pack, and neither site requires a membership to order them online.

@Texan_Reverend I've been using the box fan with a variac I have. The variac is great at dialing the speed of the box fan down to very quiet levels. I also have particulate sensors, so I know when to dial things up.

The last few years with the wildfires in California have made me a smoke mitigation expert!

https://www.amazon.com/dp/B0CZ3NTMJQ/ref=sspa_dk_detail_2?pd_rd_i=B0CZ3NTMJQ