Recently I made some upgrade and there are only three noise sources left in this system (2 low speed fans & 1 GreenPower hard disk). Below is my configuration:

Antec Solo, Noctua S12@800rpm as case fan
Seasonic X-400 fanless
Intel E8300 2.83GHz, HR01 PLUS + SFLEX-E@600rpm
Sapphire HD3650, AC S1 fanless
WD GreenPower 1.5TB EARS

The measured temperatures are listed below:
Ambient temperature is 22C.
Idle: AC Power (64W), Motherboard (36C), CPU Tcase (24C), GPU (43C), HD (29C)
Load: AC Power (127W), MB (42C), CPU (42), GPU (62C), HD (34C)
Where "Load" is to run Prime95 (Torture Test --> Blend) and run Furmark (Stability Test +Xtreme Burning mode) together for 20 minutes.

However, I met a strange issue and need your advice: I listen from ~50cm of case rear. It's very weird that if I open the side panel, the world becomes silent and I can't perceive noise in bedroom (though it's not as good as SPCR's chamber). But after close the side panel, the noise becomes significantly larger. It sounds like wind or reverberation.

What you are hearing is the effect of air resonance in an enclosed space. You can reduce the effect with acoustic foam... and quieter components. Presumably the HDD is suspended; do it if not. The Noctua is probably noisier than the sflex; try reducing its speed a bit more... or turn it off and listen again. To be fair, try turning the sflex off and listen w/ just the noctua running.

Thanks Mike!

HDD is suspended, and it's very very quiet. I will turn off the fans one by one and do some more tests.

Hi netmask254,

Nice setup,

try to boot without your hdd (livecd)

maybe cut the exhaust grid

Change the Noctua, you'll be surprised.
I just put in a Nexus 120mm fan in place of the Noctua S12 as my case exhaust. It made quite a difference in noise (maybe not in the amount of noise, but in the quality of noise for sure).

I have a single Scythe Slipstream 500rpm as exhaust in an Antec NSK3480, same problem: resonance when the side panel is on place. I think it's better to try out MikeC advise.

Regards,
Luca

See this thread.

I experienced this issue with my 5-drive Solo file server build. I believe what you're hearing is the side panel vibrating against the rest of the chassis. It is a little bit loose, especially in the middle - if you push against it with your hand and the noise goes away, then this is the problem.

To fix it I wrapped some spongy foam material I had on hand around the center of the beam supporting the power supply and taped it up so it wouldn't unravel. This resulted in a tighter seal and voila, the noise disappeared.

Lawrence, thanks for sharing your experience!

I tried this approach (i.e. push against the side panel), the noise is almost the same, thus it's not the same case with yours. I also tried opening the front door to alleviate obstacle, it doesn't help too.

What I'm going to do next is:
- Buy some new fans, existing fans were bought two years before, I can clearly hear click noise (larger than wind noise) from them especially the SFLEX-E fan (Noctua S12 is much better on this point).
- Try sound damping material. However, it's almost impossible to get any high quality product in China market. AcoustiPack is not available for retail, the only "famous" product is Akasa's PaxMate which is reviewed by SPCR and gets a very low rating. Though Lianli also sells some similar foam as that in their case, it's too thin (3mm)...