The IKEA one has three power levels, the first one is virtually inaudible, the second one hard to ignore even just being in the room during the day, the third one is really loud. Very good purifier though, looks nice, filters well. They even have a more expensive model that has Zigbee and integrates with Home Assistant.
I also hate fan noise and ended up DIYing an air purifier with computer fans as you end up with a much quieter air purifier than commercial offerings for a given CADR. If you're going this route I suggest paying a bit more and getting the noctua pwm adapter (https://noctua.at/en/products/accessories/na-fc1) so you can control the fan speed, and designing it (or using an existing design, see https://www.cleanairkits.com/products/fanless-kits and https://www.reddit.com/r/crboxes/ for inspiration) built around filters you can pick up locally. (I built mine around ikea starkvind filters, but in Canada I've never been able to get them shipped online, and the nearest ikea is annoyingly far away)
For fan choice, Arctic P12/P14 fans tend to be recommended because they're cheap and are good on paper, but they're pretty terrible acoustically (super annoying hum in the 800-1300RPM range which tends to be the optimal level just below where you can hear 120/140mm fans). I'm also irritated by fan noise and have tried a lot of different fans over the years in computers, and I've ended up just paying the Noctua tax and buying nf-a12x25s because they're one of the quietest fans, they move a lot of air with pretty good static pressure, and they don't have any humming or other acoustic issues, just the air noise as you ramp their speeds up. Phanteks T30s are even better than the noctuas and a bit less expensive, but have a bit worse noise profile (a slight drone at higher RPMs that only super picky people will even notice).
For mine I made an uglier 3 fan version of the slim 5 fan cleanairkits design using hardboard, fan grills, wood glue, a hacksaw, a drill, and a drywall knife. I'd recommend just getting it laser/waterjet cut though instead of suffering trying to cut fan holes in hardboard with a drywall knife and a small drill bit (it takes forever, and ends up being ugly AF). For power I ended up using a USB SATA adapter (noctua PWM adapter takes SATA power, need to get one that uses an external power adapter so it can output enough power, can also steal it from the air purifier if you ever actually need a usb sata adapter) and an old UL listed 12V 1.2A barrel plug power supply I found in a box of old electronics.
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