I have replaced the MB and Power supply fans with 92MM Noctua fans and the noise level dropped significantly, so I’m interested in what the noise level could/should be. I used a decimal meter on my Ender 3V2 to get an noise level. I took a reading of 60DB at the hot end and 50DB 4 ft away. It doesn’t seem to bad to me, I can work in the room when it is printing without really noticing the noise. I do have to replace the fan shroud since the original one has broken fan mounts so I can take the opportunity to change out the fans with better ones.
Noctua 40 x20 fans 20 -30 DB and $20 each. 12Volt and need buck converters
Middle of the road fans 30-40 DB $10 to $20 each. 24 Volt and just spiced in and ready to go
Other cheaper and noisier “stock” fans
So will going to the Noctua fans really make a noticeable difference over the middle of the road fans. Will a 30 to 40 DB fans really be any quieter when running. What is the difference between the “advertised” sound levels an real world experience.
I don’t expect to get the same noise reduction from small 40 mm fans like I did with the big slower fans mounted under the printer which give significantly better cooling and I cant use those big fans on a hotend. I do want good quality fans with ball bearings and maybe brush less motors.
Hey there,
Noise levels are a very preferential thing, obviously for most people the quieter the better. But noise levels bother some people more than others, personally noise levels don’t bother me so the cost of the fans has never been worth it.
DB grow on a logrithmic scale, around every 10DB the sound will double in perceived loudness. In this case it seems that the ΔDB is ~30DB decrease, this means that the sound decreased 2^3 = 8x. So with this upgrade your printer becomes about 8x quieter than before.
Hopefully this helps, if you need more explanation for this please don’t hesitate to ask,
Matthew
I can’t speak for middle of the road 24v fans, but the 4010 and 4020 noctuas that I have make almost no noise. My Noctuas have lasted around 3 years so far, and not one bit of trouble from them. Noctua makes a very good quality fan.
I wish they made a 24 V 40 x 20 fan.
I get that fan noise is an issue for some people but I can’t help feeling that noise is secondary to how much air is moved by the fan.
If I look at the Noctua NF-A4x10 FLX specifications:
https://noctua.at/en/nf-a4x10-flx/specification
best case, it moves 8.2 cubic metres of air per hours (which is a crazy measurement) and translates to 4.8 cubic feet per minute (CFM - a more common measurement) at a surprisingly high cost:
https://www.amazon.ca/40x10mm-Bearing-Premium-Cooling-NF-A4x10/dp/B009NQLT0M
and are only available to run at 12V (although there are a few boards out there, like the BigTreeTech Octopus that has a 12V LDO for fans).
The 24V fans I most recently purchased are quite a bit noisier at 10dB higher, twice as @Matthew noted. On the plus side, they run at 24V and can move 8.3 CFM of air at a quarter of the cost of the Noctua and avoid the need to generate 12V if you’re running at 24V. The Darutiox also comes with XH2.54 connectors, which means they plug in directly into most controllers (I’m not sure how the Noctua connection works - it looks like there are several options there).
https://www.aliexpress.com/item/1005004804933176.html
It would be interesting running the Darutiox fans at 60% PWM (which will give the same airflow as the Noctua) to see which is noisier.
I get that Noctua has made a name for themselves in the PC space with their quiet fans, I’m just not sure that translates into a good value in the 3D printer space; especially with the other parts making noise including the gantry moving around, the spool of filament rattling and the sound of the AC/DC cooling fan (I’m surprised how loud it is in my Mean Well supplies).
It is a valid point you have about airflow. But a properly setup hotend(I can’t speak for all metal hotends) should be able to be sufficiently cooled with a Noctua. Higher temperatures(240+) with an all metal hotend could be a different story. Ambient air temperature obviously makes a difference too. As to the Mean Well fans, well, Noctua can solve those too! 
I went a couple fan sizes up, and printed a replacement cover for the PSU in order to house it. The fan still only runs around 50% of the time, so it’s obviously cooling sufficiently. Fun fact, on the Mean Well PSUs, at least the LRS 350-24s I have, the PSU cooling fan is a 12v fan from factory.
Agreed hot ends don’t need much in the way of a fan but there is the print layer cooling fan which should have an abundance of air and I’m currently using four 4010s for cooling the stepper motor drivers and the Raspberry Pi running Klipper.
Despite that, fan noise is really overshadowed by stepper/gantry movement.
I guess YMMV as well as priorities.
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Is a 40-20 fan going to push more air through compared to a 40-10 fan. It seems like it should but things don’t always go that way.
Look at the datasheet for the fan(s) you’re interested in. I just looked up Darutiox (referenced above) for their 4020 fans:
https://www.aliexpress.com/item/1005004880094177.html
Not a significant difference when you look at the airflow out of their 4020s compared to their 4010 fans. I don’t know if this is true for all fan manufacturers but for Darutiox buying a 4020 doesn’t get you a lot more cooling.
What’s interesting is that the Darutiox 4020 is significantly quieter than their 4010 fan, basically at the same noise level of the Noctua, and almost a buck CDN cheaper for two.
No, they generally wouldn’t, but they are generally a little better then 4010s if faced with a little more back pressure.
Looks like I will go for the 40-10 mid range DB and 24V fan. Simpler.
Thats usually the route that I go as well.
Personally I like the noise, especially at night. Its like white noise except I also get cool plastic parts from it 
Matthew