1. Sound in rotating machinery is a function of "tip speed" ... the speed of the utside top of the rotating item, in fans, in fans though it's more a function of the speed of the air thru openings. When you take cover off, their air coming in has much wider area ... so it flows at lower velocities making less noise.
2. Nothing matters but the data. Just cause the company name is BeQuiet. that doesn't mean it is.
https://images.anandtech.com/doci/10837/3.png
3. AIO CLC type coolers will be louder, figure about twice as loud as a a air cooler. If it's about silence, CLC is generally not the way to go. In general, to equal or edge a decent $45 cooler's thermal performance, you will need to spend 3 times as much and be twice as loud.
https://tpucdn.com/reviews/Scythe/Fuma/images/temp_oc_aida64.png
https://www.guru3d.com/index.php?ct=articles&action=file&id=32815
4. More fans at lower rpm is better than less fans at higher rpm. 140mm fans are quieter when moving the same about of air since they will run at lower rpm and air velocity in doing so.
5. Use the provided MoBo utility to control fan speeds. Use separate channels for radiator and case fans. If you have the headers, use separate channels fpor intake and exhaust fans. Radiator fans being is used as inatkes will result in lower CPU temps and lower noise levels.
6. On all but budget boards, the MoBo fan control utility should have provisions for dampening the fan speed's response to changing temps to prevent whooshing sounds and it ramps up and down. For example, when the load is removed, the latent heat remains in the coolant ... so the utility is set to gradually reduce the fan speed over 90 seconds to get that latent heat out. Same on other side when heat is increasing ...otherwise as laod varies, control system keeps chasing it's tail so to speak. I shut the fans off when the curve calls fro speeds less than 250 rpm.
7. Don't give credence to advice saying "Oh that case has terrible airflow" when the claim is not backed up by data. You can't look at a case and make this determination. And you'd be surprised just how little impact on air flow these intuitive reasons have. And you can have a quiet case with good air flow. The 600S (based upon Evolv chassis) has great air flow and it's a quiet case. Start at 5:20. Turns out that removing the "too restrictive front cover" adds just 3% additional air flow
h ttps://
www.youtube.com/watch?v=l6RDlHueKuU&t=236s
8. Make sure all fans have rubber mounting pads; make sure of same for all storage devices, pump whatever.
9. Always question long held beliefs as things change over time .... was a time when Noctua was king but if ya take the fans off a Noctua Cooler and replace them with Phanteks, ... at the same rpm, CPU temps drop 6C
https://www.overclockersclub.com/reviews/phenteks_f140/3.htm
10. In the early days, PSUs were always at the top as we didn't have 300 watt GFX cards and the fan was used to get air out of the case. Now the bottom and behind the mobo are the more common locations.
11. Make sure that you have at least 3 intake fans for every 2 exhausts as the intakes have to push past filter restrictions.
12. A lot of the old axioms for fans are no longer as relevant .....
- "PWM fans are better cause thay have a lower cut off threshold at low rpm". This was because at low % speed, there's was not enough voltage to get DC fans moving from a dead stop and PWM is always 12v ... no longer true or at least not in many current designs. Also, you can use a PWM controlled hub and DCV fans.
- "PWM fans are noisy at low speeds.... newer designs have virtually eliminated this.
I set the fans up and test fans with the MoBo Utility.... after using the auto tune function.....
a.1 Fix pump speed at about 50%, then Run RoG Real Bench with fans at 100% speed using HWiNFO for monitoring
a.2 Make a Spreadsheet with column headers ... Pump rpm - Fan rpm - CPU Temp - Coolant Temp* - Ambient temp - Sound level
* Assuming you have a sensor
a.3 Run the Image editing or Open CL test with fans at 100% until CPU temp stabilizes and record the temps. Repeat with 90%, then 80%, then 70% down to about 30%. This should show that above a certain point, more speed is not having all that much of an effect. You will likely wind up with something rather flat and gradually increasing. Now when you play your most demanding games... see what temps you wind up with ... I see 55 - 62 in the moist demanding games, so i set the curve to go gradually up to 70C and the next point is 100% at 80C.
a.4 Keep in mind that 140mm fans in an enclosed case are inaudible below about 850 rpm. I like to use 1250 rpm as that let's me get down to about 320 rpm before fans will cut out. I have the utility shut them off below 350 rpm.
a.5 You can teak this by now addressing pump speeds the same way. Fix the fan speeds at the upper limit that you have determined is "below audible" and increase pump speeds while keeps fans fixed.
b.1 With CPU addressed, at this point, I'll switch to Furmark and address the fans and / or case fans the same way as above.
Just sitting here typing with AutoCAD and back up utility running in background ... rad fans are @ 400ish and case fans are off.